PIK3CA-Related Overgrowth Spectrum (PROS)

Literature and regulatory information updated: 17 October 2026.

PIK3CA-related overgrowth spectrum (PROS); PIK3CA-related disorders; includes CLOVES, MCAP/M-CM, fibroadipose hyperplasia (FAO/FH), hemihyperplasia-multiple lipomatosis (HHML), CLAPO, macrodactyly, facial infiltrating lipomatosis (FIL), fibro-adipose vascular anomaly (FAVA), isolated lymphatic and venous malformations, hemimegalencephaly and dysplastic megalencephaly, and Klippel-Trenaunay syndrome (KTS)

0. Initial Reference Table

1. Introduction

1.1. Clinical descriptions before molecular genetics

The first entity of the spectrum to be described was Klippel-Trenaunay syndrome. In 1900, Maurice Klippel and Paul Trenaunay published in the Archives Générales de Médecine the "naevus variqueux ostéohypertrophique", an association of a cutaneous vascular stain, varicosities and hypertrophy of bone and soft tissue of a limb [24, 25]. For decades, the disease was confused with Parkes Weber syndrome, in which clinically significant arteriovenous fistulae exist, and the two were grouped under the designation "Klippel-Trenaunay-Weber syndrome", which the classification of the International Society for the Study of Vascular Anomalies (ISSVA) now considers incorrect and discourages [25, 26]. The largest pre-molecular clinical series, from the Mayo Clinic (252 patients seen between 1956 and 1995), established the frequency of the three classical components and made conservative treatment the rule [27].

In 1997, two groups independently described children with progressive macrocephaly, capillary malformation of the face and skin resembling cutis marmorata, body asymmetry, syndactyly of the toes and hydrocephalus: Clayton-Smith and colleagues (9 children) and Moore and colleagues (13 children) [28, 29]. The entity was named macrocephaly-cutis marmorata telangiectatica congenita (M-CMTC), but the lesions are not those of cutis marmorata telangiectatica congenita, which is serpiginous, depressed and prone to ulceration; they were reticulate capillary malformations, and the disease came to be called macrocephaly-capillary malformation (M-CM) and later megalencephaly-capillary malformation (MCAP), once it was understood that the increased head circumference results from primary overgrowth of the brain [1, 30]. Megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndrome, described in the neurological literature, showed overlap with MCAP in three patients published by Gripp and colleagues in 2009, who suggested that they were the same disease [30, 31].

In 2007, Sapp and colleagues reviewed seven patients diagnosed with Proteus syndrome who did not meet the criteria for that syndrome and proposed CLOVE syndrome (congenital lipomatous overgrowth, vascular malformations, and epidermal nevi), whose bony distortion appeared only after major surgery, unlike in Proteus syndrome [32]. In 2009, Alomari characterised 18 Boston patients with a complex truncal lipomatous mass, capillary, lymphatic and high-flow malformations, paravertebral and intraspinal extension, acral anomalies and scoliosis, and added the "S" (scoliosis and skeletal and spinal anomalies) to the acronym, which became CLOVES [33]. Other phenotypes were delineated in the same period: hemihyperplasia-multiple lipomatosis (HHML), described by Biesecker in 1998, fibroadipose overgrowth (FAO), facial infiltrating lipomatosis, macrodactyly with lipofibromatous hamartoma of nerve and dysplastic megalencephaly [2, 34].

1.2. Molecular discovery

Identification of the molecular cause resulted from sequencing DNA from affected tissue, not blood. In 2011, Lindhurst and colleagues found the activating somatic variant c.49G>A, p.(Glu17Lys), in the AKT1 gene in 26 of 29 patients with Proteus syndrome, with mutant allele fractions between 1% and about 50% depending on the tissue, and concluded that the mutation would be lethal in the non-mosaic state [35]. The mosaic disease model was confirmed for PIK3CA the following year, in four publications. Kurek and colleagues identified PIK3CA variants in tissue from six patients with CLOVES, with allele frequencies of 3–30% in tissues derived from several embryonic lineages, identical to those found in cancers [36]. Lindhurst and colleagues compared, by exome sequencing, affected and unaffected cells from a patient with progressive segmental fibroadipose overgrowth and found p.His1047Leu only in the affected cells; in ten additional patients, nine had p.His1047Leu or p.His1047Arg, and the affected fibroblasts produced more phosphatidylinositol-3,4,5-trisphosphate (PIP3) [37]. Rivière and colleagues found 15 PIK3CA variants, mostly postzygotic, in 23 patients with MCAP and one with MPPH, in addition to variants in AKT3 and PIK3R2 [38]. Lee and colleagues, studying brain-blood pairs from 20 cases of hemimegalencephaly, found de novo somatic variants in 30% (PIK3CA, AKT3 and MTOR), among them the PIK3CA c.1633G>A recurrent in four cases, present in 8–40% of alleles in different brain regions [39].

Lymphatic, venous and combined malformations followed. In Boston, Luks and colleagues detected PIK3CA variants in 16 of 17 isolated lymphatic malformations, 19 of 21 KTS cases, 5 of 8 FAVA and 31 of 33 CLOVES, with five variants accounting for about 80% of the total, and concluded that PIK3CA is the most common cause of isolated lymphatic malformation [40]. In the original CLOVES study, analysis of lesional tissue from 15 patients diagnosed with "Klippel-Trenaunay-Weber syndrome" found the mosaic p.His1047Arg variant in 3 [11, 36]. Earlier genetic hypotheses for KTS, based on t(5;11) and t(8;14) translocations and on the E133K substitution in the AGGF1 (VG5Q) gene (historical notation, = NM_018046.5:c.397G>A p.(Glu133Lys), classified as benign/likely benign in ClinVar), were not confirmed: E133K was found in 3.3% of 275 healthy controls and considered a polymorphism [11, 41]. In 2016, Vahidnezhad and colleagues argued that Klippel-Trenaunay syndrome belongs to the spectrum [42].

1.3. Nomenclature and reclassifications

Before the gene was identified, the entities were treated as distinct syndromes, defined by the tissues affected. At an NIH workshop in 2013 the umbrella term "PIK3CA-related overgrowth spectrum" (PROS) was proposed, emphasising the continuum and overlap between phenotypic diagnoses; the 2015 publication presented diagnostic and testing eligibility criteria and compared the term with "22q11.2 deletion syndrome", in which a single cause unites previously separate phenotypes [1, 2]. The ISSVA glossary attributes the introduction of the term to Biesecker, in 2014, and notes that it is sometimes used for all lesions with a PIK3CA variant, including isolated lymphatic malformations, but applies more strictly to conditions with overgrowth of more than one tissue type [26].

In 2021, an international review proposed three categories: PROS, with tissue overgrowth; PIK3CA-related vascular malformations, with exclusively vascular proliferation; and PIK3CA-related non-vascular lesions. Patients who do not fit are described as "PIK3CA-related disorder" with the phenotype and function of each case [4, 5]. The 2022 international consensus, coordinated by members of ERN-ITHACA, separates two management groups after molecular confirmation: MCAP (mosaic activating PIK3CA variant, with megalencephaly and/or polymicrogyria, and overgrowth outside the central nervous system and/or vascular findings) and non-MCAP PROS (without significant megalencephaly, polymicrogyria or syringomyelia) [3]. The 2025 ISSVA classification places PROS, KTS (capillary-lymphatic-venous malformation with hypertrophy), CLOVES and CLAPO among the low-flow syndromic combined malformations, geographic capillary malformation among the manifestations of KTS and CLOVES, and reticulate capillary malformation among those of M-CM and diffuse capillary malformation with overgrowth (DCMO) [26]. For management purposes, the French 2020 PNDS keeps three designations within PROS: CLOVES, when segmental, focal or plurifocal overgrowth predominates; KTS, when vascular malformations predominate, associated with hypertrophy of the soft tissues and bone of a limb, usually the lower; and MCAP, when brain overgrowth predominates, an entity referred to a protocol of its own because it requires a specific cognitive approach [23].

Some older concepts have been superseded. The hypothesis of "paradominant" inheritance (postzygotic mutation with loss of heterozygosity in a carrier), the "obscure aetiology" and the "dominant inheritance with incomplete penetrance" of KTS, still present in a Brazilian textbook from 2021, have been replaced by the demonstration of activating somatic PIK3CA variants [1, 25, 43]. The term "haemangioma" used in old clinical descriptions of MCAP and KTS corresponds, in ISSVA terminology, to capillary or venous malformations, and not to vascular tumours [26, 29].

1.4. Definition of the entities in scope

PROS is divided into isolated forms, with a focal lesion affecting a single tissue or body part, and syndromic forms, with overgrowth and at least two other features in two systems [1]. The operational definitions used throughout this article are as follows.

2. Molecular Genetics and Pathophysiology

2.1. The PIK3CA gene and the p110α protein

PIK3CA (3q26.32; OMIM 171834; Entrez 5290; Ensembl ENSG00000121879; UniProt P42336) encodes p110α, the catalytic subunit of class IA phosphatidylinositol 3-kinase (PI3K) [6]. The enzyme phosphorylates phosphatidylinositol-4,5-bisphosphate (PIP2) to phosphatidylinositol-3,4,5-trisphosphate (PIP3), which recruits the AKT1 kinase and the phosphoinositide-dependent kinase PDPK1 to the membrane; the resulting signalling controls cell growth, survival, proliferation, motility and metabolism downstream of the receptors for insulin, epidermal growth factor (EGF), insulin-like growth factor 1 (IGF1), vascular endothelial growth factor A (VEGFA) and platelet-derived growth factor (PDGF), and is required for the development of the vascular and lymphatic endothelium [6]. The main downstream effectors are AKT and the mammalian target of rapamycin (mTOR) [1, 44].

The protein has functional domains in which activating variants cluster: the helical domain, encoded mainly by exon 9 (codons 542, 545 and 546), and the kinase domain, encoded mainly by exon 20 (codons 1044–1049) [1, 4]. Exons 10 to 14 share about 95% identity with a sequence on chromosome 22 (pseudogene), which requires assays to be designed so as not to amplify the homologous sequence [3].

2.2. Mechanism: mosaic gain of function

PROS variants are gain-of-function. Substitutions at the hotspots increase PIP3 production and AKT-mTOR signalling in a ligand-independent way, leading to cell-autonomous and non-autonomous overgrowth, aberrant adipose, vascular and lymphatic development and metabolic reprogramming [6, 37]. There is no measurable enzyme deficiency or diagnostic biochemical assay; the excess activity is confined to the cell lineages carrying the variant, which explains why the allele fraction varies between tissues of the same patient [6]. The ClinGen dosage curation (13 March 2025) assigns a score of 0 to both haploinsufficiency and triplosensitivity, and deletions or duplications of the gene should not be interpreted as a cause of PROS [1, 6].

p110α is required for the action of insulin on blood glucose and for that of IGF1, the mediator of many actions of growth hormone (GH), on tissue growth. A pathologically activated PI3Kα can mimic insulin and/or IGF1 in the cells that carry it; for a clinically relevant endocrinopathy to arise, the target tissues must carry a high variant load, which explains the picture resembling hyperinsulinism, but with suppressed insulin, observed in some infants [1, 45]. Variants in the insulin receptor or the pathway (PIK3CA, AKT2, AKT3) promote glucose uptake and utilisation and cell growth, and hypoglycaemia may be the first symptom [45].

The phenotype depends on when the mutation occurs during embryonic development, on the lineages that inherit it and on the activating strength of the variant: the earlier the mutation occurs, the greater the extent of mosaicism and, as a rule, the severity [5, 46]. The correlation between the level of mosaicism measured in a biopsy and clinical severity is, however, weak [2].

2.3. Variant spectrum and nomenclature

More than 80% of activating variants in cancer and in PROS cluster in three hotspots: Glu542 and Glu545 in the helical domain and His1047 in the kinase domain [1]. In PROS, variants are distributed throughout the gene, but the three oncological hotspots are present in more than half of cases, and a review of more than 1000 cases showed that ten recurrent variants cover about 70% of patients [4, 5]. In the series by Mirzaa and colleagues, 41 distinct variants were classified into hotspots (p.Glu542Lys, p.Glu545Lys, p.His1047Arg), strong variants (p.Cys420Arg, p.His1047Leu) and 36 variants of moderate activity [3, 8]. The following table presents the variants cited in this article with nomenclature validated in VariantValidator against the MANE Select transcript.

GeneReviews Table 9 assigns p.His1047Lys to the notation c.3141T>A; on NM_006218.4, c.3141T>A corresponds to p.(His1047Gln), so that correspondence is not used in this article [1, 7]. The variants listed in the GeneReviews tables were supplied by the authors, without nomenclature review by the GeneReviews staff [1].

2.4. Genotype-phenotype correlations

Mirzaa and colleagues studied 181 individuals with brain and/or body overgrowth (241 samples) and identified PIK3CA variants in 60 (plus 12 by other tests), distributed into three groups: severe focal overgrowth caused by strongly activating hotspot variants at low-level mosaicism; predominantly brain overgrowth, with less severe somatic overgrowth, caused by less activating variants; and intermediate phenotypes (capillary malformation with overgrowth) with intermediate variants. Sixteen of the 29 variants found were novel, and ten patients had constitutional variants [8]. Hotspots are therefore associated with very focal phenotypes (CLOVES, fibroadipose hyperplasia, lymphatic and vascular malformations, HMEG and focal cortical dysplasia), and in the brain with more severe epilepsy, whereas MCAP is associated with a wide range of variants that are less frequent in tumours [1, 3]. In the Dijon cohort (162 patients studied by ultra-deep NGS), strong oncogenic variants were present in 50.6% of patients without brain overgrowth and in 15.2% of patients with brain overgrowth (p=0.00055) [48].

2.5. Constitutional variants

A minority of patients, mainly with MCAP, have the variant in all cells. Rivière and colleagues found PIK3CA variants in the blood of 2 of 24 patients with MCAP, with the appearance of de novo germline variants, and Mirzaa and colleagues described constitutional variants in 10 patients [1, 8, 38]. The international consensus considers that its recommendations also apply to these patients, in whom blood may suffice for diagnosis and parental germline mosaicism cannot be excluded [3]. The sporadic report of germline variants is insufficient to define specific surveillance protocols [5].

2.6. Allelic disorders, curation and tumour predisposition

PIK3CA is one of the most frequently mutated oncogenes in sporadic solid tumours (breast, colorectal, endometrium, ovary, bladder, hepatocellular carcinoma, glioblastoma, head and neck squamous cell carcinoma), always through somatic variants in the tumour, and also in benign skin lesions such as epidermal naevi and seborrhoeic keratoses [1, 5]. In the COSMIC database (version 85), the p.Glu542Lys, p.Glu545Lys, p.His1047Arg and p.His1047Leu variants accounted for 80% of tumour variants [1]. The same missense variants can exist in PROS and in cancers of individuals without PROS, but GeneReviews recognises no other phenotype caused by germline variants [1].

The ClinGen gene-disease validity curation refuted, on 21 December 2023, the relationship between germline PIK3CA variants and hereditary breast carcinoma, and records no known relationship with familial ovarian cancer; GenCC concurs [6]. The OMIM entry "Cowden syndrome 5" (615108), the only one associated with the gene that is not marked as somatic, is based on a 2013 study in which 8 of 91 patients (8.8%) with Cowden syndrome without a PTEN, SDHB or SDHD variant or KLLN promoter hypermethylation had one of seven germline PIK3CA variants (five missense, one complex and one nonsense), in adults aged 27 to 71 years; the association is classified as "Limited" in GenCC, with a single submitter, and should not be treated as established [1, 6, 49]. The OMIM phenotype list also includes hemifacial myohyperplasia (606773), in which study of affected muscle from five patients found mosaic PIK3CA variants (p.Glu545Lys in two, p.Glu542Lys in two and p.His1047Arg in one), with loads of 12–25% [10]. OMIM allele descriptions use old nucleotide numbering and have internal inconsistencies (allele .0013 appears both as H1047Y, = NM_006218.4:c.3139C>T p.(His1047Tyr), and as H1047R), so the nomenclature in this article follows VariantValidator validation [7, 10]. GenCC "Strong/Definitive" submissions with autosomal dominant inheritance for MCAP describe the effect of a single altered copy (gain of function), but do not reflect the reality of a non-transmitted mosaic disease [6]. Cerebral cavernous malformations type 4 (CCM4, OMIM 619538), caused by somatic PIK3CA variants, are distinct from the familial forms due to KRIT1, CCM2 and PDCD10 [6].

2.7. The PI3K-AKT-mTOR pathway and neighbouring disorders

Overgrowth can result from activating variants in components of the pathway (AKT1, AKT3, PIK3CA, PIK3R2, MTOR) or from inactivating variants in pathway inhibitors, such as PTEN [44]. This organisation explains the clinical overlap with Proteus syndrome (somatic AKT1), PTEN hamartoma tumour syndrome and SOLAMEN syndrome (PTEN), MPPH (AKT3, CCND2, PIK3R2), Smith-Kingsmore syndrome (MTOR) and tuberous sclerosis complex (TSC1, TSC2) [1, 44, 50]. Some low-flow vascular malformations with an overlapping phenotype result from somatic variants in PIK3R1, TEK, GNAQ or GNA11, and high-flow ones from variants in genes of the RAS-MAPK pathway (KRAS, MAP2K1) [20, 51]. In mice, sirolimus was superior to alpelisib in models of vascular overgrowth caused by NRAS p.Gln61Arg, a preclinical finding that illustrates the dependence of treatment on genotype [52].

3. Clinical Spectrum and Manifestations by System

3.1. General features

The core of PROS is segmental or focal overgrowth, with or without cellular dysplasia, of congenital or early childhood onset, mainly affecting the brain, limbs (including digits), trunk and face, usually asymmetrically [1]. Unilateral involvement is more frequent than bilateral, and the overgrown tissues often have a "ballooned" appearance on the digits and the dorsum of the hands and feet [1]. In an NIH cohort of 35 patients with segmental overgrowth and a PIK3CA variant, overgrowth was congenital in 31 (89%), asymmetric and disproportionate in all, with adipose dysregulation in all, predominantly left-sided, more in the lower limbs and progressing from distal to proximal; there were vascular malformations in 15 (43%) and epidermal naevi in 4 (11%), and in the most severe cases adipose tissue was lacking in unaffected regions [17]. Lipomatous overgrowth may be ipsilateral or contralateral to the vascular malformation [1].

3.2. Isolated forms

The following table brings together the isolated phenotypes by organ or tissue described in GeneReviews.

Source: [1]. The international consensus adds to the localised spectrum muscular overgrowth with ectopic accessory muscles and hemi-orofacial asymmetry with enlarged peripheral nerves and perineuriomatous pseudo-onion bulbs [3].

3.3. Syndromic forms

Source: [1]. The capillary malformation helps to guide the subtype: a malformation with geographic borders, dark red or purple and well demarcated, is typical of CLOVES and KTS, whereas a reticulate, pink to light red, poorly defined malformation is typical of MCAP and DCMO; a persistent midfacial capillary stain suggests MCAP and capillary malformation of the lower lip, CLAPO [5, 26].

3.3.1. CLOVES

The characteristic truncal lipomatous mass infiltrates neighbouring tissues and often requires surgical excision [1]. Paravertebral and intraspinal extension, more frequent in CLOVES than in other forms, exposes the patient to the risk of compression of the spinal cord, thecal sac and roots, with major neurological deficits, including myelopathy; high-flow paravertebral lesions can cause spinal cord ischaemia [1, 33]. Lipomatosis may invade the hip joints, intravertebral spaces, muscle, viscera (liver, spleen, pancreas), intestine and mediastinum, and coexist with regional reduction of adipose tissue elsewhere [1]. Renal malformations are frequent (pyelectasis, dilated ureters, hydronephrosis, duplicated renal arteries, cysts, enlarged kidneys) [1]. CLOVES carries a particular risk of a postoperative hypercoagulable state and of thromboembolism associated with thoracic or central phlebectasia [1, 2].

3.3.2. MCAP

In MCAP, adult head circumference (HC) lies between +2 and +10 standard deviations (SD) above the mean [1]. In a review of 21 children, HC at birth was typically +2 to +7 SD for gestational age, increased in SD during the first year in most and could stabilise in early childhood, usually remaining ≥+3 SD; some patients have normal HC at birth and develop progressive macrocephaly in the first year [1]. More than 90% of those affected have congenital megalencephaly of a progressive nature, sometimes detected on prenatal ultrasound with or without ventriculomegaly and with a thick corpus callosum [1]. In a review of 65 children with MCAP, 37 (56%) had ventriculomegaly, ranging from mild to frank hydrocephalus, and 15 had cerebellar tonsillar ectopia, with or without herniation [1, 53]. More than half of affected children undergo ventricular shunting or endoscopic third ventriculostomy, usually in the first year, and after shunting head growth continues to accelerate, confirming the primary nature of the megalencephaly [1]. Tonsillar ectopia, unlike ventriculomegaly, is rarely congenital, is associated with the rapid brain growth of infancy and regressed spontaneously in two patients due to accelerated cranial growth; syringomyelia is common [1, 30]. Polymicrogyria, present in more than 50% of children, is mainly bilateral perisylvian and is associated with epilepsy, oromotor dysfunction (feeding, swallowing and expressive language), delay and tone abnormalities [1, 3].

Most children with MCAP have some degree of ID, usually mild to moderate and with slower continuous progress; fewer than 10% have severe disability, without regression [1, 30]. Among 21 children, six had autistic traits or a diagnosis of autism spectrum disorder (ASD) [1]. Younger children with frontal polymicrogyria are hypotonic and may have pseudobulbar problems; older children often develop spasticity [1]. Connective tissue dysplasia causes joint hypermobility, hyperelasticity, soft, velvety, lax skin and thick subcutaneous tissue [1, 30]. Structural heart defects (atrial and ventricular septal defects), anomalies of the great vessels and arrhythmias have been described [1, 30]. MPPH is distinguished from MCAP by the absence of facial capillary malformations and cutis marmorata, cutaneous syndactyly, connective tissue dysplasia and focal overgrowth [2, 46]. The French national protocol for MCAP (HAS, 2021) brings together the diagnostic and follow-up recommendations for megalencephaly and the differential diagnosis with the other monogenic macrocephalies [54].

3.3.3. Other syndromic forms

In FAO, fibroadipose overgrowth is segmental and progressive, and skeletal overgrowth preserves bony architecture, unlike in Proteus syndrome [1, 37]. HHML is static or mildly progressive and has sometimes been confused with Proteus syndrome [34]. Facial infiltrating lipomatosis has a detectable variant in all tissues studied, with allele fractions of 1.5–53% [3, 55]. Lymphatic malformations may form part of complicated lymphatic anomalies, especially generalised lymphatic anomaly, which has an aggressive course and an unfavourable prognosis when close to vital structures of the head and neck [1, 56]. In a series of isolated lymphatic malformations, the variant was detected in 79% of cases, with allele fractions of 0.1–13% [3].

3.4. Klippel-Trenaunay syndrome

KTS is characterised by congenital or early childhood hypertrophy of a limb, with low-flow capillary, venous and lymphatic malformations in any area, more on the legs, buttocks, abdomen and lower trunk, predominantly unilateral but not infrequently bilateral [25]. The lower limb is affected in about 95% of cases and the upper in 5%; the reference textbook gives bilaterality in 15%, percentages that are not mutually exclusive [25]. The characteristic venous anomaly is the lateral marginal vein, a persistent embryonic vein that begins as a venous plexus on the dorsum and lateral side of the foot and extends proximally [25, 57]. The PNDS describes the typical course of this marginal venous system: it arises on the dorsum of the foot, runs up the lateral side of the leg and the outer or posterolateral aspect of the thigh and usually drains into the femoral or iliac veins, sometimes the internal iliac; it coexists with a deep venous system that may be hypoplastic or hypertrophic and, having no valves, has very slow or stagnant flow [23]. The affected limb has no signs of high flow and its temperature is normal or only slightly increased when stasis is marked, which helps to separate KTS from Parkes Weber syndrome [23]. According to the protocol, which does not give the denominator, superficial or deep venous thrombosis, with embolic potential, affects about 10% of patients, especially in pregnancy, after surgery or after a vascular procedure; episodes of acute pain due to phleboliths in cavitary venous malformations are frequent and respond better to anti-inflammatory drugs or to heparin for a few days than to analgesics, and phlebalgia due to inflammation of the venous wall may occur [23]. Ectasia of the high popliteal vein is frequent in KTS and rarely causes symptoms [23].

In the Mayo Clinic cohort (252 patients, 136 women and 116 men, 1956–1995), there was capillary malformation in 98%, varicosities or venous malformations in 72% and limb hypertrophy in 67%; 63% had the complete triad and 37% two of the three components, and 72% had atypical veins (lateral vein or persistent sciatic vein) [27]. These percentages coincide with those of the Brazilian chapter on the disease, which adds that capillary malformation tends to be the first manifestation, that 75% of patients develop manifestations before 10 years of age, that leg length discrepancy ranges from 1 to 12 cm and worsens with age, and that lower gastrointestinal bleeding occurs in 1–12% [43]. The Mayo Clinic series predates molecular genetics and probably includes cases that would now be reclassified, since KTS is not a genomically uniform diagnosis: many severe cases have a PIK3CA variant, others with GNAQ or GNA11 variants fit better into DCMO, and those with higher-flow anomalies fit into Parkes Weber syndrome [26, 27]. The PNDS likewise recognises that not all cases of KTS have a PIK3CA variant, recommends the same management with or without an identified variant and proposes the inclusion of negative cases in research programmes [23].

The frequency of the lateral marginal vein depends on the population and the method. In a Dutch cohort of 70 patients studied by duplex ultrasound, it was present in 12 (17.1%), and the authors proposed using only the terms "persistent lateral marginal vein" and "persistent sciatic vein", together with the status of the deep venous system [57]. In a Chinese series of 58 patients (63 lower limbs, 2020–2022), the lateral marginal vein was present in 60 limbs (95.2%), with a mean diameter of 5.23 mm, and there were deep venous anomalies in 25 (39.7%); vein diameter correlated with clinical venous severity (tau 0.338; p<0.001) and lymphatic malformation was associated with greater severity [58]. The differences reflect different inclusion criteria and techniques.

In the Brazilian cohort from Santa Casa de São Paulo (58 patients, April 2007 to October 2008, mean age 12.8 years), labelled by the authors as "Klippel-Trénaunay-Weber", port-wine stain was present in 93.1%, bony or soft tissue hypertrophy in 86.2% and venous changes in 72.4% (varicose veins in 56.8%); leg length discrepancy was present in 77.5% (3–30 mm; mean 11.5 mm), exceeded 25 mm in 10% and required orthopaedic surgery in no case; there was pain in 68% (80% of these due to venous stasis), oedema in 53%, stasis ulcers in three patients and arteriovenous fistulae in 4 of 47 studied by imaging [59]. The inclusion of arteriovenous fistulae and the designation used indicate that the series mixes KTS and Parkes Weber syndrome, a separation that ISSVA requires [26].

Complications of KTS include thrombophlebitis, skin ulcers and infections, lymphoedema, bleeding from visceral malformations (rectum, bladder, oesophageal varices), localised intravascular coagulopathy and thromboembolism [25, 43]. In a Dutch cohort (48 of 68 patients, median age 43 years), 17% (95% CI 8.7–30%) had had deep vein thrombosis (DVT) or pulmonary embolism (PE), 48% superficial venous thrombosis, 23% abnormal perfusion scintigraphy and 4.2% chronic PE, without chronic thromboembolic pulmonary hypertension [60]. Quality of life (SF-36 and Skindex-29) in 78 Dutch patients with KTS was lower than that of the general population on all scales except mental health and emotional role, and lower than that of other chronic diseases for physical function and pain [61]. Orphanet maintains an entry for inverse KTS (ORPHA:329324), and the Italian consensus describes, among PIK3CA-related manifestations, segmental underdevelopment, with hypoplasia of a limb associated with cutaneous signs and lymphatic or venous malformations [5, 9].

3.5. Manifestations by system

3.5.1. Central nervous system

The degree of ID appears to relate mainly to the presence and severity of seizures, cortical dysplasia and hydrocephalus, and gross motor delays are multifactorial (megalencephaly, cortical malformations, hypotonia, limb asymmetry or overgrowth, connective tissue dysplasia) [1]. Epilepsy occurs in about 30–40% of individuals with PIK3CA variants, with focal and tonic-clonic seizures, among others; type, severity, age at onset and electroencephalographic changes depend on the tissue distribution of the variant and on cortical malformations [1]. The international consensus states that the exact incidence is unknown and that it affects up to 50% of children with bilateral cortical malformations, a figure not specific to PROS [3]. In a series of 21 patients with megalencephaly and delay or ASD, the developmental quotient was lower in those with a variant in the PI3K-AKT-mTOR pathway (62.8 versus 76.1; p=0.021) [3].

Tonsillar ectopia presents in the infant with irritability, drooling, difficulty swallowing and respiratory problems, especially central apnoea, and in the child with neck pain, headache, motor weakness, sensory changes, visual problems, dysphagia and behavioural changes [1]. Chiari malformation and syringohydromyelia may progress within 2–3 years and involve the whole spinal cord [3]. Brain MRI may show, in addition to megalencephaly, perisylvian and insular polymicrogyria, cortical dysplasia, a thick corpus callosum, cavum septum pellucidum or cavum vergae, white matter T2 hyperintensity, dilated dural venous sinuses and prominent perivascular spaces [30]. Pituitary hypoplasia and pituitary stalk interruption have been described [5]. In CLOVES, lipomatous extension into the paravertebral and intraspinal spaces may compress the spinal cord, dural sac and roots; the PNDS adds the risk of low tethered cord and neural tube defects and describes transitional forms between CLOVES and MCAP, with macrocephaly and brain malformations (polymicrogyria, cortical dysplasia, hemimegalencephaly, ventriculomegaly, Chiari malformation type 1, dysplasia of the corpus callosum) that may cause ID and epilepsy [23].

3.5.2. Vascular malformations, coagulopathy and thrombosis

The vascular malformations are capillary, venous and, less often, arterial or mixed; low-flow ones (lymphatic and venous) overlap the truncal or limb overgrowth, and many are identified only by MR angiography or MR venography [1]. In one cohort they were present in 59% of patients [3, 62]. Cutaneous capillary malformations appear in the midline of the face (persistent nevus simplex) or in a generalised reticulate pattern; venous malformations, including venous aneurysms, may grow and cause bleeding, pain and disfigurement; high-flow (arteriovenous) malformations occur mainly in the spinal and paravertebral regions [1].

The risk of DVT and PE is increased, especially in combined capillary-lymphatic-venous malformations, and rises after surgery or sclerotherapy; contributing factors are chronic stasis, immobility, dehydration, reduced anticoagulant proteins and the effect of the variant on the endothelium [1, 63]. The international consensus cites DVT frequencies of 17% and PE frequencies of 14–22%, with 64% of events occurring after surgery or sclerotherapy, and dural sinus venous thrombosis and stasis in MCAP [3]. Localised intravascular coagulopathy (LIC) is a chronic consumptive coagulopathy of extensive low-flow malformations, with raised D-dimers and low fibrinogen; ISSVA defines it as an entity different from the Kasabach-Merritt phenomenon, which consists of severe thrombocytopenia and hypofibrinogenaemia due to platelet trapping in infants with kaposiform haemangioendothelioma or tufted angioma [26]. GeneReviews and some older descriptions mention "haemangiomas" and a risk of Kasabach-Merritt syndrome in the KTS phenotype; in current terminology, the haematological picture of the venous malformations of KTS corresponds to LIC [1, 26]. According to the PNDS, chronic LIC, attributed to blood stasis in the malformations and/or an endotheliopathy due to mTOR pathway hyperactivity, presents with D-dimers above 500 ng/mL in about half of patients; in extensive malformations, activation of coagulation may consume fibrinogen and, to a lesser extent, platelets, in a picture similar to disseminated intravascular coagulation (DIC) [23]. The same protocol considers DVT rare and accepts systematic screening for coagulopathy (platelets, fibrinogen, D-dimers) in extensive vascular forms, although the age at which to perform it and the benefit for thromboembolic prevention have not been assessed [23].

3.5.3. Lymphatic system, infection and other local complications

Internal or external lymphatic malformations cause swelling, pain and sometimes local bleeding after trauma; cutaneous vesicles with lymphatic leakage are a portal of entry for infection [1, 34]. Recurrent cellulitis and lymphoedema are among the vascular complications described [5]. Pleural effusions occur mainly during or after pneumonia [3]. The PNDS distinguishes macrocystic from microcystic lymphatic malformations, the latter more prone to recurrent inflammatory flares; aseptic autoinflammatory flares, linked to hyperactivity of the PIK3CA-AKT-mTOR pathway, are much more frequent than infections and should not be confused with them [23]. Intracystic haemorrhage in a macrocystic malformation causes acute pain and often leads to secondary involution of the cyst [23].

3.5.4. Musculoskeletal system

The hands are broad, spade-like, with widely spaced fingers or ulnar deviation and overgrowth of one or more digits; the feet show overgrowth with a wide sandal gap, bulbous toes, dorsal and plantar lipomatous masses and a broad forefoot [1]. Patterning defects include postaxial, preaxial or central polydactyly and cutaneous syndactyly of the toes (patterns 2-3, 2-4 and 2-5) and sometimes of the fingers [1]. Knee dislocation, leg length discrepancy, chondromalacia, scoliosis, vertebral anomalies, spina bifida and pectus anomalies occur, the latter mainly in CLOVES [1, 5]. The PNDS adds talipes equinovarus, hip dysplasia, block syndactylies and divergence of the digits, and mentions pectus excavatum and postaxial polydactyly as occasional; progressive scoliosis, of variable severity, is the most common skeletal anomaly, and excessive bone growth may cause significant leg length discrepancy, with repeated surgery [23].

3.5.5. Kidney and genitourinary system

Renal malformations are frequent, especially in CLOVES; FAO is associated with testicular or epididymal cysts and hydrocele; cryptorchidism and central hypogonadism have been described in patients with brain involvement [1, 3]. Hydronephrosis, hydroureter, urinary incontinence and haematuria are among the functional features that justify PIK3CA testing [2]. The PNDS also mentions renal lithiasis, haematuria (sometimes due to venous lesions of the bladder) and splenic lesions, and notes that some visceral anomalies result from lipomatous infiltration or from deep lymphatic or venous malformations [23].

3.5.6. Skin

Cutaneous findings include linear keratinocytic epidermal naevi, which may follow dermatomes or Blaschko lines, seborrhoeic keratoses, benign lichenoid dermatosis, café-au-lait macules, hypopigmented macules, mosaic hyperpigmentation, dermal melanocytic naevi, acrochordons and, in MCAP, cutis marmorata and lax skin [1, 5].

3.5.7. Endocrine system

Endocrine problems affect a minority and have only been described in patients with brain involvement: hypoglycaemia, mainly hypoinsulinaemic and hypoketotic, GH deficiency (in a significant minority of patients with MCAP), central hypothyroidism, central hypoadrenalism and central hypogonadism [1, 3]. The hypoglycaemia is a clinical phenocopy of congenital hyperinsulinism, but plasma insulin during hypoglycaemia is undetectable, ketone bodies and fatty acids are suppressed and hepatic glycogen is preserved, which explains the glycaemic response to glucagon; some patients have detectable insulin [3, 64]. It is diagnosed mainly in the neonatal period, but may appear later (first episode at 6 years in a boy with MCAP) and may improve with age [1, 3].

3.5.8. Tumours

The most common benign tumours are vascular and lipomatous (lipomas, sometimes multiple and stable); meningiomas have been described in two children with MCAP (21 months and 5 years), spinal and major nerve neurofibromas, ovarian cystadenomas and uterine fibroids [1, 3]. The frequency of Wilms tumour has been estimated at 1.4–3.3%; in a set of 12 patients with Wilms tumour or nephroblastomatosis (8 with CLOVES, 2 with MCAP and 2 with KTS), the mean age at diagnosis was 27.4 months (median 18; range 9–119), 7 had Wilms tumour, 4 lesions indeterminate between Wilms and nephroblastomatosis and 1 nephroblastomatosis, and 6 had hotspot variants [1]. In the Boston series of 122 patients with CLOVES (1998–2016), there were 4 Wilms tumours (3.3%), all diagnosed by 2 years of age, compared with about 1 in 10,000 in the population [65]. In a series of 89 patients with DCMO (67), M-CM (17) or an indeterminate phenotype (5), there were no cases, with the limitation that some patients were under 8 years at last follow-up [66]. In KTS, none of 115 institutional patients had Wilms tumour, the literature contained 1 case in 1363 patients and the National Wilms Tumor Study Group recorded no KTS among 8614 patients with Wilms [67].

The Dijon cohort (267 patients with PROS) recorded 6 cancers (2.2%), with a cumulative probability of 5.6% at 45 years (95% CI 1.35–21.8%); combining literature and cohort, there were 6 Wilms tumours or nephrogenic rests (0.12%) and 4 other cancers in 483 patients with a proven variant, mainly with p.His1047Leu or p.His1047Arg [68]. Isolated cases of leukaemia, vestibular schwannoma, retinoblastoma, meningioma and papillary intralymphatic angioendothelioma have been described, and kaposiform haemangioendothelioma appears among the locally invasive tumours, without sufficient data to establish a causal association [1, 5]. Elevated urinary cell-free DNA with a PIK3CA variant correlated with nephroblastomatosis or Wilms (p<0.05), and PIK3CA alleles were detected in the urine of 6 of 17 patients with CLOVES (35%) and of none of 24 with KTS [3].

3.6. Natural history and treated disease

The first radiological assessment of natural history included 30 patients from Lyon and Paris (of 67 screened, 2008–2021), with a confirmed variant and at least two MRIs ≥2 months apart, without surgery, interventional radiology or targeted therapy; 43.3% were children and the median age at first MRI was 19 years (interquartile range 5–34) [69]. Over a median follow-up of 75.7 months (2.1–160.3), 25 patients (83.3%) had progressive disease according to RECIST criteria, with a median increase of 36.6% (2.6–230.7%) and a median annualised rate of 7.2% per year (0.6–40.1%), and progression was frequent in adulthood [69]. The expert group consulted by the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) indicated that spontaneous regression is not expected and that lesions tend to progress without intervention, and the CHMP noted the lack of pre-treatment natural history data [21]. These data from untreated patients are the comparator for interpreting the single-arm studies in section 7; the results of patients treated with surgery, sirolimus or alpelisib are described in that section.

Typical KTS follows a relatively favourable course without treatment or with elastic compression alone; disproportionate growth may require epiphysiodesis or removal of a phalanx, and major surgery is rare [25, 27]. Significant neurological involvement (DMEG, HMEG) is associated with an unfavourable prognosis [1].

4. Clinical Recognition and Warning Signs

4.1. When to suspect

PROS should be considered with overgrowth of any tissue (brain, adipose tissue, vessels, muscle, bone, nerve), capillary, venous, arteriovenous or mixed vascular malformations, lymphatic malformations, epidermal naevi or hyperpigmented macules, single or multiple digital anomalies of the hands or feet (macrodactyly, syndactyly, polydactyly, sandal gap), renal malformations and benign tumours, or with brain MRI showing focal overgrowth with or without cortical dysplasia (HMEG, focal cortical dysplasia, DMEG) [1]. Family history is usually negative (isolated cases) [1]. The NIH workshop defined as an indication for PIK3CA testing the presence of at least one of the following features: a congenital spectrum or congenital isolated feature from the diagnostic criteria; combined vascular malformation (extensive capillary, lymphatic or venous malformation); congenital musculoskeletal overgrowth; a patterning defect (polydactyly, sandal gap, syndactyly, broad spade-like hands with ulnar deviation, symmetric digital overgrowth without a nerve pattern, ligamentous laxity, creased palms and soles, overgrown feet with bulbous toes and lipomatous masses, broad forefoot, knee dislocation, limb discrepancy, chondromalacia patellae); a congenital central nervous system anomaly (polymicrogyria, megalencephaly, hydrocephalus, Chiari, syrinx); congenital epidermal naevus; congenital soft "doughy" skin or hypermobility; with or without functional features such as hydronephrosis, urinary incontinence, haematuria, constipation, gastrointestinal bleeding, epilepsy, ID, autism or hypoglycaemia [2].

Examination of a child with asymmetry should measure lengths and circumferences using fixed bony landmarks. Some asymmetry is common in the population, but a difference of more than 1 cm in the length of a limb, with a measurable difference in circumference, should be considered abnormal [70]. The upper limb is measured from the acromion to the tip of the middle finger with the arms hanging; the lower limb from the greater trochanter to the floor when standing or to the lateral malleolus in the infant; circumferences are measured at the greatest diameter or from a fixed bony point (for example, 10 cm below the lower border of the patella) [70]. It is not always clear which side is normal: hemihypertrophy is more common in a child with normal development or a large child, and hemihypoplasia suggests chromosomal mosaicism [70]. The examination looks for café-au-lait macules, mosaic pigmentation, vascular marks, epidermal and connective tissue naevi (the latter suggest Proteus syndrome, especially on the soles), lymphatic malformations, lipomas, tongue asymmetry, signs of Beckwith-Wiedemann syndrome, syndactyly and macrodactyly [44, 70]. In macrocephaly, the combination of limb asymmetry, syndactyly and capillary malformation of the philtrum points to M-CM, and parental HC adjusted for stature helps to exclude familial macrocephaly [46].

4.2. Recognition by age

4.3. Warning and emergency signs

The emergency signs are as follows: signs of raised intracranial pressure or ventricular shunt dysfunction; signs of brainstem or spinal cord compression (apnoea, dysphagia, neck pain, limb weakness, regression), especially in MCAP and in CLOVES with intraspinal extension; status epilepticus; hypoglycaemia with episodic irritability, hypotonia, loss of consciousness or seizures; chest pain, dyspnoea or sudden asymmetric oedema, suggesting PE or DVT, especially after surgery, sclerotherapy or immobilisation; fever with cellulitis over a lymphatic malformation, which may progress to septic shock; bleeding from a visceral malformation; respiratory distress with pleural effusion [1, 3, 47]. Developmental regression requires treatable causes to be excluded (shunt dysfunction, tethered cord, worsening Chiari, syrinx or hydrocephalus) [3].

4.4. Newborn screening

There is no newborn screening for PROS. Neonatal hypoglycaemia is detected through the general criteria for blood glucose screening in the newborn, which include macrosomia, malformation and a family history of a genetic cause of hypoglycaemia [45].

5. Diagnosis: Criteria, Tests and Algorithms

5.1. Clinical diagnostic criteria

The diagnosis is established in a patient with suggestive findings and a mosaic or, rarely, constitutional activating pathogenic PIK3CA variant [1]. The 2015 NIH workshop criteria, adopted by the 2022 international consensus, require the mandatory conditions and the features of group A or group B [2, 3].

Source: [2]. All patients described up to 2015 were sporadic and mosaic; progression is frequent but not mandatory, and group B requires congenital or early onset [2]. After molecular confirmation, the 2022 consensus allocates patients to the MCAP and non-MCAP PROS management groups described in section 1.3 [3]. The French PNDS adopts the same criteria for CLOVES and KTS, requires overgrowth to be segmental and not generalised and accepts a presumptive diagnosis when the variant is not identified; it notes that seborrhoeic and benign lichenoid keratoses, included in the criteria because they can carry PIK3CA variants, are not classical manifestations of PROS, and anticipates the future inclusion of frequent signs such as syndactyly and sandal gap [23].

5.2. Clinical diagnosis of KTS

KTS is diagnosed clinically by the combination of capillary malformation and venous malformation, with or without lymphatic malformation, and overgrowth of a limb [26]. The classical rule of at least two of the three components (capillary malformation, varicose veins or venous malformation, hypertrophy) is based on pre-molecular series, in which 63% had all three [27, 43]. A Dutch group proposed restrictive criteria, according to which limb growth may be increased or decreased, small arteriovenous fistulae may exist and varicose veins are not mandatory [71]. ISSVA separates KTS from Parkes Weber syndrome, characterised by arteriovenous shunts, and from DCMO, with mild and proportionate overgrowth [26]. MRI is the non-invasive technique of choice for characterising the malformations, and duplex ultrasound assesses the lateral marginal vein and the integrity of the deep venous system [3, 25, 57].

5.3. Molecular testing: sample

Most variants are postzygotic and not present in blood, so DNA from clinically affected tissue is preferred: fresh skin biopsy over the affected area (ideally with vascular malformation in a region of overgrowth), surgical excision specimen of the overgrown tissue or uncultured tissue [1, 3]. The recommendations of the VASCERN VASCA group specify at least 4 mm of affected tissue, obtained at debulking surgery or by skin biopsy with abnormal vasculature, fresh, frozen or formalin-fixed paraffin-embedded (FFPE), with histological examination to confirm representativeness and dissection of the epidermis to enrich the sample [20]. DNA should be extracted without culture, because fibroblast culture may select for or against the mutated clone; FFPE tissue can be used with lower yield and a risk of contamination at the microtome [2, 3, 5]. Before any surgery, the patient should be referred to genetics and tissue should be saved for testing [5]. The PNDS gives preference to biopsy of a skin lesion identified as pathological; without a skin lesion, it proposes skin biopsy in a hypertrophic area or ultrasound-guided biopsy of a deep lesion, more often vascular, makes use of surgical resections and accepts repeating the sampling in another tissue if the phenotype is very suggestive and the first result negative [23].

Blood is not recommended as a routine sample [1, 20]. MCAP is the exception: variants are sometimes detectable in blood or saliva, with lower yield than skin, and the international consensus proposes a two-step approach, with tissue biopsy only if blood or saliva are negative (some families prefer to start with the biopsy) [3, 5]. In MCAP, DNA from saliva or skin fibroblasts has a higher detection rate than peripheral blood; in HMEG, focal cortical dysplasia and DMEG, brain tissue obtained at epilepsy surgery has a higher detection rate than peripheral tissues [1]. In KTS, confirmation of the variant may be difficult, tissue obtained at surgery offers the best chance and the variant should be demonstrated if an inhibitor is being considered [3].

Circulating cell-free DNA (cfDNA) in urine, plasma or lymphatic fluid is promising but less sensitive: urinary droplet digital PCR (ddPCR) is limited to about five hotspots, produces false negatives due to allelic heterogeneity and fractions of 0.001% that are difficult to interpret, and there is no recommendation for diagnostic use [3, 20].

5.4. Molecular testing: techniques and analytical sensitivity

GeneReviews recommends targeted capture of the entire PIK3CA coding region, followed by very deep coverage NGS, to detect very low levels of mosaicism across the whole gene; targeted deletion and duplication analysis is not recommended, because all PROS variants are gain-of-function [1]. The statement that sequencing identifies 100% of pathogenic variants refers to the proportion of known variants the method is able to detect, not to clinical sensitivity, which depends on the tissue and the level of mosaicism [1]. The techniques differ in detection limit and breadth.

Standard-depth exome sequencing may miss mosaic variants, especially in blood, and Sanger sequencing is only useful when the allele fraction is relatively high (about 20%) [1]. The variant allele fraction (VAF) is the proportion of reads carrying the variant; the percentage of carrier cells is approximately twice the VAF, and a constitutional heterozygous variant has a VAF close to 0.5 [3]. In VASCERN centres, about 15% (41 of 262) of cases with a pathogenic PIK3CA variant had a VAF below 3%, and laboratories use minimum thresholds of 1–3% [20]. Technical recommendations include unique molecular identifiers (UMIs), common polymorphisms to detect cross-contamination, validation of all variants with VAF <5% by digital PCR or a second NGS, and digital PCR for recurrent variants [20]. Orthogonal validation is unnecessary when the variant appears in more than one tissue; the international consensus indicates Sanger for VAF ≥20%, pyrosequencing for ≥5% and ddPCR for ≤5%, and the Italian consensus Sanger for VAF ≥10% [3, 5]. Assay design must discriminate the homologous sequence on chromosome 22, for example with upstream long-range PCR [3].

Hotspot screening by ddPCR or commercial oncology assays is a reasonable first approach in macrodactyly, CLOVES and KTS, but leaves about 30% of patients without a diagnosis; the Italian consensus therefore recommends a panel that includes, in addition to PIK3CA, AKT1, AKT2, AKT3, PTEN, CCND2, GNAQ, GNA11, MTOR, PIK3R1, PIK3R2, TSC1, TSC2, RPTOR, RICTOR, TEK, RASA1, HRAS, KRAS, NRAS, SOS1, ARAF, BRAF, MAP2K1, PTPN11 and CBL [1, 5]. The VASCERN core list has 24 genes and requires the complete PIK3CA as the minimum mandatory region [20]. Exome or genome sequencing, on an appropriate sample, is reserved for atypical phenotypes [1].

5.5. Diagnostic yield and limitations

Yield is lower in very localised forms, such as isolated macrodactyly, and depends on the tissue, the quality and site of the sample, the technique and the depth [3, 5]. A negative result does not exclude the clinical diagnosis [1, 3]. In the face of a negative result, the international consensus recommends reassessing the sample quality, the tissue, the detection limit and the clinical diagnosis; there is no evidence on how many rebiopsies are justifiable [3]. In the Melbourne study, the sequence of ddPCR, Sanger, high-depth exome and reanalysis of clinical exome increased the yield [51].

5.6. Report content and interpretation

The report should state the gene and the transcript with version (NM_006218.4 for PIK3CA), the variant in HGVS nomenclature, the VAF, the coverage, the regions below the quality threshold, the genes analysed, the tissue studied and the limitations, and the classification according to the ACMG/AMP criteria adapted to somatic variants in vascular anomalies [20]. A VAF close to 50% in several tissues suggests a constitutional variant and should prompt germline testing and counselling [3, 20]. Variants should be shared in public databases (ClinVar, LOVD) [20]. Classification of rare variants outside the hotspots relies on recurrence in PROS or cancer and on functional data; rare variants have been grouped into strong, intermediate and weak according to activity [2, 8]. Family segregation is of no use in a non-transmitted mosaic disease, and deletions or duplications of the gene are not a cause of PROS [6].

5.7. Initial assessment after diagnosis

Sources: [1–3]. In CLOVES, the assessment includes perioperative coagulation studies and histopathology of resected lesions [6].

The PNDS grades the initial assessment according to extent: in limited forms, such as isolated macrodactyly, investigations are confined to the affected segment [23]. The history records functional and aesthetic discomfort, previous surgery, the frequency of inflammatory flares and infections, pain, bleeding, body image perception and daily impact; the examination includes photographs and measurements to assess progression, and a lower limb length difference of up to 1.5 cm is considered almost physiological [23]. Duplex ultrasound is the first-line investigation for a vascular lesion, although less informative and harder to interpret in the infant, and is complemented by MRI directed at hypertrophic or suspicious areas (cervicofacial, thoracic, abdominopelvic, limbs), to detect deep lymphatic, venous, digestive or genitourinary malformations and characterise the extent of the overgrowth [23]. The suggested MRI protocol identifies pathological fat on T1 and slow-flow malformations on fat-saturated T2, with T1 and fat-saturated T2 sequences in two planes and, if necessary, post-contrast T1; it adds MR venography when there is ectasia of the deep venous system and considers arterial angiographic sequences useless in the great majority of cases, because high-flow lesions are rare [23]. In the young child, the timing of MRI is weighed against the need for general anaesthesia and the therapeutic consequences of the result [23]. Spinal MRI looks for tethered cord or neural tube closure defect when there is a sacral dimple, gluteal cleft anomaly or abnormal neurological examination, and in the neonatal period spinal ultrasound may be used; limb radiographs, lower limb radiographic measurement (especially before puberty), spinal radiographs and weight-bearing radiographs for discrepancy should favour low-radiation systems, such as EOS, with simultaneous biplanar acquisition [23]. Baseline echocardiography and electrocardiography look for cardiovascular malformations and rhythm disturbances and allow right-sided pressures to be monitored in venous malformations with embolic potential [23].

5.8. Biochemical diagnosis of hypoglycaemia

Suspected hypoglycaemia justifies an inpatient fasting test under endocrinology, with collection of critical samples [3]. The general criteria for hyperinsulinaemic hypoglycaemia are blood glucose <2.5–3 mmol/L, insulin ≥1 µIU/mL and C-peptide ≥0.2 ng/mL during hypoglycaemia, low ketone bodies and non-esterified fatty acids, and a rise in blood glucose >1.7 mmol/L (30 mg/dL) 30–40 minutes after 1 mg of glucagon; in disorders of insulin signalling, such as PROS, insulin is low or undetectable, with hypoketotic hypoglycaemia and a response to glucagon [3, 45]. Confirmed hypoglycaemia requires measurement of GH and cortisol and a dynamic test of the hypothalamic-pituitary-adrenal axis [3].

5.9. Prenatal diagnosis

PROS enters the differential of fetal overgrowth with megalencephaly, fibroadipose overgrowth, pleural effusion or ascites [3]. In MCAP, ultrasound may show fetal overgrowth and progressive macrocephaly without maternal hyperglycaemia or fetal hyperinsulinism, ventriculomegaly, pleural effusions, polyhydramnios, hydrops, limb asymmetry and frontal bossing; fetal MRI has described diffuse bilateral polymicrogyria and polysyndactyly [1]. Prenatal molecular testing in a pregnancy with an ultrasound suspicion is possible, but is limited by mosaicism, because the sampled tissue (villi or amniocytes) may not contain the variant [1, 3]. In CLOVES and KTS, the French PNDS bases prenatal suspicion on segmental tissue hypertrophy, often extensive, with cystic lesions, extensive lymphatic malformation or anomalies of the extremities; macrocephaly suggests a transitional form with MCAP, and the case should be presented to a multidisciplinary prenatal diagnosis centre [23]. If the variant is sought in amniotic fluid, the protocol recommends analysing uncultured and cultured fluid, because variants appear to be detected preferentially in cultures, probably due to the clonal advantage they confer in vitro, unlike what is recommended for postnatal tissues; a negative result does not exclude the diagnosis [23]. As these forms rarely cause neurological disability, the prenatal prognosis is based on the extent of the hypertrophy and of the vascular malformations on ultrasound and fetal MRI, information that guides counselling, including a possible request for termination of pregnancy for medical reasons [23].

5.10. Practical algorithm

In the presence of congenital segmental overgrowth or combined vascular malformation, the pathway proposed by the sources consulted is as follows: confirm congenital or early onset and the mosaic pattern and exclude signs pointing to another diagnosis (cerebriform connective tissue naevus and postnatal onset in Proteus syndrome; arteriovenous fistulae in Parkes Weber syndrome; macrocephaly with genital pigmentation and a family history in PTEN hamartoma tumour syndrome; macroglossia and omphalocele in Beckwith-Wiedemann syndrome) [1, 2]; obtain uncultured affected tissue (blood or saliva first only in MCAP) and request deep NGS of the whole PIK3CA gene or a panel with a threshold of 1–5% [3, 20]; if negative, review the sample, tissue and diagnosis and consider a second tissue, targeted ddPCR or high-depth exome [3, 51]; after confirmation, classify as MCAP or non-MCAP PROS and complete the systemic assessment in section 5.7 [3]. In isolated hemihyperplasia without signs of PROS, study of 11p15 is recommended to stratify Wilms tumour screening, according to the Beckwith-Wiedemann spectrum criteria [44].

6. Differential Diagnosis

6.1. Comparative table

Sources: [1, 6, 26, 34, 43, 44, 70, 72–74].

6.2. Proteus syndrome

Proteus syndrome was described by Cohen and Hayden in 1979 and individualised by Wiedemann in 1983, who named it after the polymorphous Greek god [75]. Joseph Carey Merrick, the "Elephant Man", is now considered a probable case [34]. It is the main differential of syndromic PROS and is distinguished by its natural history: most patients have modest or absent manifestations at birth, the first manifestations appear between 6 and 18 months, mainly on the feet and hands, and progression is rapid and continuous in childhood, with stabilisation after adolescence; fewer than 5% present with prenatal HMEG [34, 75]. In an affected area, overgrowth progresses in a typical way (15% larger at 1 year, 30% at 3 years, 100% at 6 years), and the bones become distorted, with irregular calcification, even where there is no vascular malformation [34]. The cerebriform connective tissue naevus is almost pathognomonic, rare in the infant, and appears on the soles, hands, alae nasi, ear and near the lacrimal puncta; it should not be confused with the prominent plantar or palmar creasing of other forms of overgrowth, and no patient with PROS in the NIH series had it [2, 34]. The predisposition to DVT and PE is marked and PE is the most common cause of death; in the NIH cohort, projected mortality is 25% before 20–22 years of age [34, 75]. The French PNDS estimates that Proteus syndrome is about 100 times rarer than CLOVES and highlights three guiding features: absence of congenital manifestations, appearance of the plantar cerebriform naevus and rapidly progressive course [23].

The 2019 consensus criteria require three general criteria (mosaic distribution, sporadic occurrence and progressive course) and a score ≥10 with a mosaic AKT1 variant or ≥15 without a variant; with a variant and a score between 2 and 9 the term AKT1-related overgrowth spectrum is used [34, 76]. The negative criteria discriminate PROS directly: substantial prenatal extracranial overgrowth and "ballooning" overgrowth subtract 5 points each [34].

Source: [34]. Biesecker's 1999 criteria (mosaic distribution, progressive course and sporadic occurrence, with one A criterion, two B or three C) were replaced by this version [70, 77]. Targeted analysis of AKT1 c.49G>A in a skin biopsy of affected tissue detects the variant in about 50% of probands; the variant has been identified in the blood of only two patients, and the methodology must detect allele fractions below 1% [34]. In PROS, growth-promoting and procoagulant drugs are also avoided, as in Proteus syndrome [34].

6.3. PTEN hamartoma tumour syndrome and SOLAMEN

PTEN hamartoma tumour syndrome brings together Bannayan-Riley-Ruvalcaba syndrome in childhood and Cowden syndrome in the adult; birth weight is usually >+2 SD, but macrocephaly predominates (HC above the 99.6th centile), with ASD or ID in some patients, vascular malformations, lipomas, pigmented macules of the penis and mucocutaneous lesions, and in the adult an increased risk of thyroid (mainly follicular), breast and endometrial tumours [44, 74]. SOLAMEN syndrome (segmental overgrowth, lipomatosis, arteriovenous malformation and epidermal naevus) results from a germline PTEN variant with a second mosaic somatic variant, and is associated with cancer risk and with ovarian cystadenoma, multiple breast tumours, thyroid adenomas, gingival papules and multinodular goitre [1]. Older articles described PTEN variants in patients with "Proteus syndrome", now considered carriers of PHTS [74]. According to the PNDS, the benign ovarian, breast and thyroid tumours of SOLAMEN usually show biallelic PTEN inactivation, and Bannayan-Riley-Ruvalcaba syndrome does not usually have segmental overgrowth outside the lipomatous areas, which separates it from CLOVES [23].

6.4. Parkes Weber syndrome and capillary malformation-arteriovenous malformation

Parkes Weber syndrome combines a cutaneous capillary malformation with multiple underlying arteriovenous microfistulae and soft tissue and skeletal hypertrophy of the affected limb, and continues to be misdiagnosed as KTS [72]. In the RASA1 spectrum, the capillary malformations are multiple, small (1–2 cm), pinkish, round or oval, sometimes with a white halo and pink centre, and 75.4% of carriers have capillary malformations and 44.9% arteriovenous malformations or fistulae; more than 50% of AVMs are located in the face and/or brain, including vein of Galen aneurysmal malformation in the infant, and high-flow lesions may cause haemorrhage, steal ischaemia and heart failure [72]. Brain imaging is recommended to identify treatable macrofistulae before symptoms [72]. RASA1 variants are mainly truncating (92%) or deletions (8%), with haploinsufficiency and a second somatic hit in the lesion; they were described in 68 families in a 2013 series [72, 78, 79]. ISSVA classifies CM-AVM as autosomal dominant due to RASA1 (CM-AVM1) or EPHB4 (CM-AVM2) and places Parkes Weber syndrome among the low-resistance capillary malformations, separate from KTS [26]. In KTS, a clinically significant arteriovenous shunt is not characteristic [25]. The PNDS stresses that the vascular malformations of PROS are only very rarely high-flow, whereas Parkes Weber syndrome and CM-AVM result from autosomal dominant germline variants in RASA1 or EPHB4, with multiple superficial or deep arteriovenous fistulae that may affect the brain and spinal cord [23].

6.5. Other differentials

MPPH shares megalencephaly, polymicrogyria and hydrocephalus with MCAP, but has no vascular malformation or syndactyly; it results from AKT3, PIK3R2 or CCND2 variants, more often de novo germline, and shares the central nervous system surveillance recommendations [3, 46]. In perisylvian polymicrogyria, the panel should include GPR56, AKT3, PIK3CA, PIK3R2, WDR62 and testing for the 22q11.2 deletion [80]. Encephalocraniocutaneous lipomatosis, described by Haberland and Perou in 1970, is distinguished by naevus psiloliparus and intracranial lipomas; two thirds of patients have normal intelligence, seizures occur in about 50% and the findings do not progress, except for bone cysts and jaw tumours [73]. Isolated hemihyperplasia may result from 11p15 alterations in about 20% of cases, with embryonal tumours in 9 of 168 patients (5.9%) and Wilms tumour in 3% in a multicentre study [70]. Familial angiolipomatosis and Proteus syndrome may be confused with NF1 [81]. In facial asymmetry in childhood, ECCL and Proteus syndrome enter the differential of FIL, together with the sphenoid wing dysplasia of NF1 [82]. In the classification of primary lymphatic dysplasias, KTS and CLOVES belong to the syndromic forms of the PI3K-AKT-mTOR pathway, alongside Parkes Weber syndrome (RASA1), Hennekam syndrome and Milroy disease [83, 84].

7. Treatments and Risk Management Strategies

7.1. Organisation of care

There is no curative treatment [1, 5]. Care should be coordinated in a tertiary centre by a multidisciplinary team, usually led by a paediatrician experienced in rare genetic diseases, including surgeons (plastic, orthopaedic, vascular, neurosurgeon), interventional radiologists, geneticists, dermatologists, pathologists and a haematologist-oncologist [1, 5]. The 2022 international consensus is the main management reference; the 2023 Italian consensus adds surgical, rehabilitation and transition recommendations, and the VASCERN documents guide genetic testing and the management of venous malformations [3, 5, 20, 85]. Topics without international consensus are orthopaedic and debulking surgery, surgery of vascular and lymphatic anomalies, bleeding, inflammation and infection, pain, interventional radiology and physiotherapy [3]. The French 2020 PNDS organises care for CLOVES and KTS in reference or competence centres with experience in segmental overgrowth and complex vascular anomalies, coordinated by a physician from the centre, and sets out three principles: therapeutic decisions are taken at a specialised multidisciplinary meeting; debulking surgery is no longer the mandatory option; and inappropriate management can have serious consequences, which justifies dedicated clinics [23]. The social worker is involved from diagnosis; the family doctor ensures access to diagnostic confirmation and to a follow-up plan in a nearby centre, checks that follow-up is provided by a qualified team and is the first point of contact for complications, in coordination with the reference team [23].

7.2. Supportive treatment by manifestation

Rehabilitation should start early, with physiotherapy for range of motion and trophism, orthotic aids before and after surgery and fine motor training in macrodactyly [5]. Physiotherapy prevents late orthopaedic complications (contractures, scoliosis, hip dislocation); hypertonia or dystonia can be treated with baclofen, tizanidine, botulinum toxin or orthopaedic procedures [1]. Psychological assessment of the patient and family should take place soon after diagnosis, with individual sessions in adolescence [5].

The PNDS proposes a stepwise approach to pain. The first step is to distinguish an inflammatory flare, infection, superficial or deep thrombosis and haemorrhage into a macrocystic lymphatic component, with ultrasound and, if necessary, MRI [23]. For painful flares due to inflammation of microcystic lymphatic components and for superficial thrombosis of a venous ectasia, it indicates a non-steroidal anti-inflammatory drug (NSAID) for 3 to 5 days, once underlying infection has been excluded; LMWH may relieve pain if the NSAID fails, and chronic pain justifies testing for LIC (D-dimers and fibrinogen) in order to institute prolonged LMWH if LIC is confirmed, with the aim of limiting fibrinogen consumption [23]. Analgesics are chosen according to the level of pain, with the support of a pain clinic when drugs are combined or step 2 or higher analgesics are used, and non-pharmacological measures may be added [23]. Intracystic haemorrhage is treated with an analgesic, with or without an NSAID, and only rarely with evacuating aspiration [23].

For infections, fever with suspected erysipelas requires blood cultures and starting an antibiotic; infections of lymphatic malformations are treated with a prolonged oral antibiotic, for 14 to 21 days, preferably a beta-lactam, with a macrolide or pristinamycin in case of allergy, and some patients need the intravenous route [23]. For recurrent infections, prolonged antibiotic prophylaxis with the same classes may be proposed, after distinguishing them from recurrent autoinflammatory flares [23]. Anaemia due to chronic losses is treated with iron and, if severe, with transfusion [23].

The PNDS does not give doses. The reference doses from the official sources used for comparison, with the extrapolation indicated, are as follows.

The 2019 HAS recommendation advises against adjuvant NSAIDs in bacterial dermohypodermitis, so the PNDS NSAID is reserved for inflammatory flares and superficial thromboses in which infection has been excluded [23, 86].

7.3. Vascular and lymphatic malformations in PROS and KTS

In KTS, elastic compression is indicated for all patients, and superficial venous intervention (stripping, saphenectomy, sclerotherapy, ablation) is only performed after patency of the deep venous system has been confirmed [3, 27, 59]. The lateral marginal vein, more frequent in KTS, is associated with venous hypertension and thromboembolism, and its treatment is justified after confirming the integrity of the deep venous system [3]. In a retrospective series of 44 children with KTS (mean age 12.5 years, single centre), 1940 nm endovenous laser ablation of symptomatic marginal veins was technically successful in all, with post-procedural pain in 90.9% and mild skin complications in 95.5%, resolved in about one month, late recanalisation in 4.5%, no DVT or PE, and improvement in the venous quality of life index (828.4 to 1562.1; p<0.001); this is a single-arm study without a control [89]. The authors of the Brazilian cohort advised against surgery for the fistulae because of poor results [59]. Lower gastrointestinal bleeding requires identification of the source; mild cases are treated with a high-fibre diet, hydration and iron, and recurrent bleeding with haemodynamic compromise may require surgery [43]. The PNDS indicates compression for vascular malformations of the limbs, to improve venous haemodynamics and symptoms and, potentially, to prevent superficial thrombosis: made-to-measure stockings or sleeves, circular or flat knit, at least class III, with pressures that increase with limb volume, adapted to the predominant venous or lymphatic component and layered if necessary, with more frequent renewal than usual because of lympho-haematic leakage [23]. Multilayer bandaging treats trophic disorders due to venous hyperpressure and oedematous flares not controlled by the garment, and elevation and mobilisation of the limb are advised on long journeys sitting down [23]. Manual lymphatic drainage is only useful in pitting lymphoedema, not in cystic lymphatic malformations, in which lymph does not circulate; cutaneous and mucosal lymphatic vesicles require enhanced hygiene and can be treated by sclerotherapy, CO₂ laser, cautery or excision, to reduce leakage and infection [23]. Capillary malformations can be lightened with pulsed dye laser on aesthetic request, long-pulse Nd:YAG laser serves troublesome or exudative superficial malformations, and laser coagulation treats venous bladder lesions with haematuria [23].

In sclerotherapy of lymphatic and venous malformations, OK-432, doxycycline, bleomycin, bleomycin A5, ethanol and sodium tetradecyl sulfate are used, with complications such as fibrosis and oedema with mass effect; other options are cutaneous and endovascular laser, manual lymphatic drainage, compression and cryotherapy [5]. The risk of DVT and PE increases after surgery and sclerotherapy, so these procedures require prior haematological assessment (section 7.4) [1, 3]. The French national protocol for cystic lymphatic malformations (HAS, 2021) presents the results of sclerotherapy by agent, sirolimus doses and the treatment regimen for inflammatory flare-ups [90].

In interventional radiology, the PNDS reserves percutaneous sclerotherapy for focal venous or lymphatic lesions with recurrent pain and proposes percutaneous obliteration of marginal veins by embolisation or endovenous laser photocoagulation; it considers endovascular radiofrequency ablation of the lateral marginal vein to be of little efficiency and occlusion of large ectasias of the deep venous system, especially the supra-articular popliteal vein, to be debatable, because these rarely cause thromboembolism and the procedure may make some patients worse [23].

In surgery, the PNDS weighs the indications, especially the most mutilating ones, against pharmacological therapies that may avoid them [23]. Volume reduction of bulky lymphatic malformations with hypertrophy aims at mobility, quality of life, aesthetics or avoiding compressions that compromise musculoskeletal development; the patient should be informed of the risk of local recurrence, the need for several interventions and the often keloid and retractile scarring, and volume and length reductions of the feet should preferably begin before walking age [23]. Reduction of adipose hypertrophy is often carried out in several stages and is difficult on the palms and soles, because of the proximity of neurovascular and tendinous structures; liposuction is debatable, because of the dense and highly vascularised fat and the risk of fat embolism and infection [23]. Venous or lymphatic malformations inaccessible to interventional radiology are treated by ligation of persistent embryonic veins, phlebectomy or stripping [23]. In the extremities, epiphysiodesis is planned before the end of growth, according to bone age and the discrepancy to be corrected; realignment osteotomy, ray resection or amputation may be considered in major overgrowth with chronic pain and disability, shortening of digital rays may avoid amputation and allow footwear, correction of thumb deviation favours pinch and footwear, and syndactyly and polydactyly are operated on according to functional need [23]. Severe scoliosis is operated on after brace failure, maxillofacial asymmetry with malocclusion is treated by plastic or maxillofacial surgery, and a perimedullary vascular and adipose mass with weakness, urinary incontinence or severe constipation justifies neurosurgery, despite the risk of recurrence due to usually partial resection [23]. In inguinal hernias and testicular ectopia, the possibility of a lymphatic malformation with retroperitoneal extension makes surgery lengthy and requires careful dissection near the spermatic cord; in refractory gastrointestinal bleeding, partial colectomy, anorectal mucosectomy or ligation of ectatic veins may be proposed [23]. Wound healing may be of poorer quality than in the general population [23].

7.4. Thrombosis, coagulopathy and perioperative care

All patients with a venous malformation should have a baseline haematological assessment, with coagulation and D-dimers, which serve as useful screening for DVT and PE; there is no specific biomarker of thrombotic risk in PROS [1, 3]. The international consensus cites the recommendation of the vascular anomalies group of the American Society of Pediatric Hematology/Oncology (ASPHO): D-dimers more than five times normal should be corrected with therapeutic-dose low-molecular-weight heparin (LMWH) for at least 2 weeks before and after surgery or sclerotherapy; with lower D-dimers, prophylaxis as in Proteus syndrome is suggested, with enoxaparin 0.5 mg/kg (the consensus does not specify the frequency; no maximum dose defined in the source), sequential pneumatic compression until ambulation and early mobilisation; there is no evidence supporting routine anticoagulation, and confirmed DVT or PE is treated according to the American College of Chest Physicians guidelines [3]. The VASCERN pathway for venous malformations grades management: normal D-dimers require no action; high D-dimers with normal fibrinogen justify considering LMWH in the presence of pain, before surgery, sclerotherapy or other procedures, in pregnancy or with thromboembolic risk (abnormal echocardiogram, pulmonary symptoms); high D-dimers with low fibrinogen require discussion with haematology (LMWH, fibrinogen) [85]. The Italian consensus reserves anticoagulation for high-risk situations or previous DVT [5]. In CLOVES, the risk of postoperative hypercoagulability is particular, and GeneReviews indicates anticoagulation for thrombosis and fresh frozen plasma for coagulopathy [1].

The French PNDS details perioperative care of extensive vascular malformations, especially venous ones. The bleeding risk depends on the coagulopathy, and not only on the venous nature of the malformation, and LMWH has a dual purpose: to prevent thrombosis and to prevent bleeding, by controlling the DIC triggered by surgery [23]. Before any procedure, in addition to the full blood count, prothrombin time and activated partial thromboplastin time, fibrinogen and D-dimers are measured; postoperative prevention with LMWH for 15 days to 4 weeks is prescribed in all cases and extended to the pre- and perioperative periods when D-dimers are raised [23]. A fall in fibrinogen indicating DIC leads to administration of fibrinogen concentrate perioperatively and to consideration of LMWH if bleeding is not controlled by transfusion, fibrinogen and other haemostatic agents, because LMWH halts the activation of coagulation that consumes fibrinogen and platelets; surgery requires a haemostasis opinion and red cell concentrates available in theatre, and prevention is adjusted to the personal and family thrombotic history, bleeding complications and the course of haemostatic parameters [23]. Outside surgery, prolonged prophylaxis with LMWH may be proposed when thromboses cause recurrent inflammatory flares with raised D-dimers and low fibrinogen [23]. For the PNDS, only heparins, and LMWH in particular, are effective in LIC: vitamin K antagonists and antiplatelet agents have no effect, and experience with direct oral anticoagulants is limited, with less correction of the biological abnormalities of LIC; it therefore does not recommend direct oral anticoagulants for DVT, superficial thrombosis or PE, which it treats with LMWH [23]. The reference doses of enoxaparin are given in section 7.2.

7.5. Central nervous system

The decision on shunting, endoscopic ventriculostomy or posterior fossa decompression rests with a team including a paediatric neurosurgeon familiar with the disease; stable, asymptomatic tonsillar ectopia is managed non-surgically, and decompression is reserved for brainstem compression or syringomyelia [3]. The GeneReviews authors observed that, in MCAP, hydrocephalus may be treated more successfully by third ventriculostomy, a personal observation without a comparative study [1]. In epilepsy, surgery (hemispherectomy or focal resection) is considered when there are focal findings on imaging, EEG or semiology; the ketogenic diet is an option with level B evidence [1, 3].

7.6. Endocrinopathies

Parents should be alerted to the signs of hypoglycaemia (episodic irritability, hypotonia, loss of consciousness, seizures) [3]. Acute hypoglycaemia is treated with intravenous glucose, sugary drinks or glucagon, and prevented with frequent meals, cornstarch or modified starch and, in severe cases, overnight enteral or parenteral feeding; continuous glucose monitoring is useful when there is a risk, but some devices are incompatible with MRI [1, 3]. For insulin-mediated neonatal hypoglycaemia, the consensus mentions somatostatin or diazoxide, and for intractable forms dependent on intravenous glucose the exploratory use of sirolimus and/or a PIK3CA inhibitor (grade C evidence) [3]. Central hypothyroidism is treated with levothyroxine monitored by FT4 and not by TSH, and adrenal insufficiency with hydrocortisone [3]. GH deficiency may justify a trial of GH, which GeneReviews and the international consensus suggest deferring until after 2 years of age, to avoid the main period of brain growth, with monitoring of linear growth and of the overgrowth trajectory; at least four cases with a response have been described, and the risk of tumorigenesis is theoretical [1, 3, 91]. The PNDS describes, in some patients with CLOVES or KTS, difficulty gaining weight, with a contrast between hypertrophic and hypotrophic areas without an established explanation, which may justify nutritional support and tends to improve with age and sometimes after surgical reduction of large lipomatous masses; hypoglycaemia is exceptional and limited to severe forms of CLOVES [23]. Thyroid function is assessed in the presence of weight gain, mood changes or reduced activity [23].

7.7. Alpelisib (Vijoice®)

7.7.1. Rationale and first data

Alpelisib (BYL719) is a selective PI3Kα inhibitor. In 2018, Venot and colleagues showed, in a postnatal mouse model of PROS/CLOVES, that the drug prevented and improved organ dysfunction, and then treated 19 patients with PROS on a compassionate use basis: all had symptomatic improvement, previously intractable vascular tumours decreased, congestive heart failure improved, hemihypertrophy reduced and scoliosis lessened, without substantial adverse effects [92]. The series is observational and uncontrolled. The same active substance is authorised in oncology as Piqray®, in combination with fulvestrant, for advanced hormone receptor-positive, HER2-negative breast cancer with a PIK3CA variant, with different doses and label; the two brands are not interchangeable [6, 19, 93].

7.7.2. Indication, presentations and dosage

In the United States, Vijoice® is indicated for adult and paediatric patients aged 2 years or older with severe manifestations of PROS who require systemic therapy, under accelerated approval based on response rate and duration of response; continued approval of the indication may depend on verification of clinical benefit in confirmatory trials [18]. In the European Union, the indication covers patients aged 2 years or older with severe or life-threatening manifestations of PROS who require systemic therapy, and treatment should be initiated by a physician experienced in the management of PROS [19]. Neither indication requires a companion diagnostic, but demonstration of the variant was an inclusion criterion in the trials and is recommended before considering an inhibitor [3, 6, 21].

Sources: [18, 19]. Tablets can be taken whole or suspended in water (2–4 ounces, or 1–2 ounces for a tube), left to stand for about 5 minutes, crushed and administered within 60 minutes, orally or via a nasogastric tube (French 5–12, silicone or polyurethane) or gastrostomy (French 12–24) [18]. The granules are only for the 50 mg daily dose, without combining sachets, using partial sachets or mixing with tablets; they can be placed directly on the tongue with 2–4 ounces of water or dispersed in 1–3 teaspoons of water, milk, apple juice, apple puree or yoghurt, or administered via a tube with 20 mL of water [18, 19]. A missed dose can be taken up to 9 hours late; after vomiting the dose is not repeated on the same day [18]. A meal increases the area under the curve by 73–77%; time to maximum concentration is 2–4 hours, steady state is reached in 3 days, the predicted half-life is 8–9 hours, and elimination is by hydrolysis and CYP3A4, with 81% in faeces and 14% in urine [18].

7.7.3. Adverse effects and their management

In EPIK-P1 (57 patients; 95% exposed ≥6 months and 79% >1 year), there were serious adverse reactions in 12% (dehydration and cellulitis, two patients each), discontinuation in 11% and dose reduction in 5% [18]. Reactions with a frequency ≥5% were diarrhoea (16%), stomatitis (16%), hyperglycaemia (12%), eczema (7%), dry skin (7%), alopecia (5%), headache (5%) and cellulitis (5%, grade 3–4 in 3.5%); the most frequent laboratory abnormalities were decreased corrected calcium (60%), decreased phosphate (59%; grade 3–4 in 5%), increased glucose (56%; grade 3–4 in 11%), haemoglobin A1c (HbA1c) ≥5.7% (38%), increased creatinine (31%) and increased bilirubin (29%) [18]. In the EPIK-P1 publication, adverse events occurred in 82.5% and drug-related events in 38.6%, mainly hyperglycaemia (12.3%) and aphthous ulcer (10.5%), with no deaths [94]. In the 6–17-year paediatric group of EPIK-P2, with a median exposure of 26.4 months and a median mean daily dose of 105.6 mg, the adverse events of special interest were gastrointestinal toxicity (42.7%), hypersensitivity (18.3%), stomatitis (15.9%), rash (15.9%), alopecia (13.4%), hyperglycaemia (7.3%) and pancreatitis (3.7%), and there was grade ≥3 growth retardation suspected to be drug-related in two patients (2.4%) [21]. In children aged 2–5 years in EPIK-P2 (n=7), there was grade ≥3 pneumonia in 28.6% and serious events in 42.9% [21]. There were no deaths attributed to alpelisib in the EPIK-P1, P2 and P3 studies [21]. A case of hyperosmolar hyperglycaemic coma in a patient with PROS has been published [95].

Source: [18]. Decisions on hyperglycaemia are based on fasting blood glucose [18]. The antidiabetics indicated in the label are metformin in adults and children aged 10 years or older, and sodium-glucose cotransporter 2 (SGLT2) inhibitors or insulin sensitisers (thiazolidinediones or dipeptidyl peptidase 4 inhibitors) only in adults [18]. Administration of an antihistamine before the onset of rash may reduce its incidence and severity [18]. The EU adds that treatment should not be started in patients with a history of severe cutaneous adverse reactions [19].

7.7.4. Monitoring, interactions and special populations

Fasting blood glucose and HbA1c are measured before starting; fasting blood glucose is repeated at least once a week for the first 2 weeks and then at least every 4 weeks, and HbA1c every 3 months, more often in the presence of risk factors (body mass index ≥30, raised fasting blood glucose or HbA1c, systemic corticosteroids, age ≥75 years); if hyperglycaemia occurs, blood glucose is checked at least twice a week until it normalises and, on an antidiabetic, weekly for 8 weeks and then every 2 weeks [18, 19]. Safety has not been established in uncontrolled type 1 or type 2 diabetes [18]. Data on growth and development are insufficient, so regular monitoring of children's growth and development is recommended; in rats, thickening of the growth plate, reduction of trabeculae and thinning of dentine were observed [18, 19]. The European risk management plan includes the effects on bone and dental growth in children and the risk of osteonecrosis of the jaw, described with Piqray® in combination with bisphosphonates or RANKL inhibitors [21]. Strong CYP3A4 inducers and breast cancer resistance protein (BCRP) inhibitors should be avoided [18]. The French PNDS, which predates the authorisations, considers hypersensitivity, ongoing pregnancy and fasting blood glucose ≥140 mg/dL (≥7.7 mmol/L) or HbA1c >6.4% to be contraindications to PIK3CA inhibitors; the current labels only contraindicate hypersensitivity (severe, in the FDA label) and treat uncontrolled type 1 or type 2 diabetes as a situation of unestablished safety, requiring glycaemia to be optimised before starting [18, 19, 23].

In animals, alpelisib caused post-implantation loss, low fetal weight and skeletal malformations at exposures similar to human ones, and there are no data in pregnant women [18]. Pregnancy should be excluded before starting; women use effective contraception during treatment and for 1 week after the last dose, and men with a partner of childbearing potential use condoms for the same period; breastfeeding is not advised during treatment and for 1 week after [18, 19]. In the EU, because it is not known whether alpelisib reduces the efficacy of systemic hormonal contraceptives, women using them should add a barrier method [19]. The drug may impair fertility, according to animal data [18].

7.8. Regulatory status

Sources: [16, 18, 19, 21, 96–98]. No medicinal product was authorised in the EU for PROS before Vijoice® [5, 16]. The sources consulted include no information on marketing or reimbursement in Portugal by INFARMED, and a search found no registration of Vijoice® with the Brazilian Health Regulatory Agency (ANVISA), which does not demonstrate that none exists. In Italy, the 2023 consensus mentions early access to medicines through the Italian Medicines Agency (AIFA) and free care for rare diseases through the national health service [5]. In France, the 2020 PNDS, which predates any authorisation, provided for alpelisib through a named-patient temporary authorisation for use, under a therapeutic use protocol, in severe life-threatening forms or when mutilating surgery was planned, and gave priority to inclusion in trials, because of the safety monitoring they provide; the 2026 European authorisation has made outdated the protocol's statement that no drug is authorised for this indication [19, 23].

The divergent position of seven CHMP members considered the database small and heterogeneous, EPIK-P1 retrospective, without internal control, single-centre and in compassionate use, EPIK-P2 a failed study and EPIK-P3 limited, without demonstration of durability or clinical relevance, and EPIK-P4 a single-arm study with the same endpoint; it acknowledged the unmet medical need and the mechanistic rationale [98]. The CHMP considered the effect in EPIK-P2 "modest" and its clinical relevance "questionable" [21].

7.9. Clinical trials and targeted therapy studies

Sources: [18, 19, 21, 62, 94, 99–105].

Comparison between these studies has limits. EPIK-P1 is a retrospective review of patients on compassionate use, with favourable selection and no internal control, and the difference between 27% and 37.5% results solely from how patients without assessment are handled [21, 106]. EPIK-P3 included 40 of the EPIK-P1 patients who perceived benefit and did not use standardised assessment [21]. EPIK-P2, the only placebo-controlled study, did not meet the primary endpoint in either group; the controlled period lasted only 16 weeks, the population was broader than the approved indication (severity was not required), adults started at 125 mg instead of the labelled 250 mg and the comparison with placebo was a secondary endpoint not formally tested [21]. The mean reduction in target lesion volume was 4–8%, and the proportion of patients with any reduction at week 16 was 83.0% versus 51.9% in adults and 69.8% versus 31.8% in children, indicating that some reductions also occur on placebo [21]. The studies used their own volumetric criteria, because the lesions have atypical growth and irregular shape, and patient-reported outcomes may be more appropriate than imaging [4, 106]. Untreated natural history, with progression in 83.3% and median growth of 7.2% per year, is the implicit comparator for the single-arm studies [69]. The zovegalisib and serabelisib results come from press releases and media reports and do not allow comparison with alpelisib.

7.10. Sirolimus

Sirolimus (Rapamune®), an mTOR inhibitor, is used off-label in PROS and in complicated vascular anomalies [1, 5]. In the pooled three-centre study (39 patients aged 3–48 years, mean age 16.6 years), the dose was titrated to a target trough plasma concentration of 2–6 ng/mL according to renal transplant algorithms; the mean concentration achieved was 3.4 ng/mL (95% CI 3.1–3.7), with a mean daily dose of 1.2 mg once daily in capsules in adults and 0.58 mg twice daily in oral solution in children [62]. The effect was greater in actively growing tissues and in adipose overgrowth, with no effect on quality of life or on skin lesions [62]. There were related adverse events in 28 of 39 patients (72%), 37% of these grade 3–4, and grade ≥3 events in 13 (33%); infections in 16 (41%), haematological abnormalities in 8 (21%), grade 4 neutropenia, interstitial pneumonitis and sirolimus hypersensitivity syndrome with prolonged fever, and 7 patients (18%) were withdrawn for adverse events [62]. Withdrawal criteria included neutropenia <1.0×10⁹/L (United Kingdom and France) or <0.5×10⁹/L (USA), 3+ proteinuria, alanine aminotransferase (ALT) >3 times the upper limit of normal, glomerular filtration rate <70 mL/min/1.73 m², pneumonitis, severe or recurrent infections and QTc prolongation; live vaccines were excluded from 4 weeks before to 6 weeks after treatment [62]. The authors recommend case-by-case decisions [62]. In other series of vascular anomalies, toxicity included hypercholesterolaemia, hypertriglyceridaemia, raised transaminases, mouth ulcers, thrombocytopenia, bacterial and opportunistic infections and gastrointestinal symptoms, and in a series of extensive cervicofacial lymphatic malformations the response rate was 91% [5]. Durable responses are uncommon and there is recurrence after discontinuation [107]. The VASCERN pathway presents sirolimus as an emerging option in venous malformations [85]. Gonadal effects are usually small and reversible, according to the 2023 joint VASCERN-VASCA and ASPHO statement (section 8) [108]. The PERFORMUS study (NCT02509468; 63 patients with superficial low-flow vascular malformations) ended in 2019 without results posted in the registry [109]. The French PNDS considers that publications on sirolimus suggest an effect on pain more than on the volume of the hypertrophied limb, that many did not confirm the molecular diagnosis, and that the open-label trial of 39 patients (described in the protocol as CLOVES), with a 7% volume reduction after 6 months, no change in quality of life and significant adverse effects, does not show a fully satisfactory benefit-risk ratio; it recommends that the decision be taken by a multidisciplinary reference team with the patient or their representatives, according to the alternatives, and with enhanced monitoring [23, 62]. It lists as contraindications to mTOR inhibitors pregnancy and breastfeeding, lack of effective contraception during treatment and for up to 12 weeks after discontinuation, hypersensitivity, current or suspected malignancy, active infections requiring antibiotics or antivirals or uncontrolled, active hepatitis B or C virus or HIV infection (caution if past hepatitis infection), a history of active tuberculosis (caution if past infection), active pneumopathy, chronic liver disease (AST or ALT >3 times normal), chronic kidney disease stage ≥3 (GFR <60 mL/min), neutropenia <1.0×10⁹/L and uncontrolled dyslipidaemia [23]. The hepatic and neutrophil thresholds coincide with the withdrawal criteria of the pooled study, whose renal threshold (<70 mL/min/1.73 m²) is more stringent [23, 62]. Topical sirolimus has been described in cases of cutaneous lymphangiectasia, with a randomised trial under way at the date of the protocol [23].

7.11. Other pathway inhibitors

Taselisib, a class I PI3K inhibitor, was tested in the TOTEM trial at 1 mg and then 2 mg per day; the trial was stopped because of two unexpected serious adverse reactions, and the safety profile precludes prolonged use [101]. Miransertib (MK-7075, ARQ 092), an allosteric pan-AKT inhibitor, was administered in MOSAIC at 15 mg/m² per day in cycles 1–3 of 28 days and then at 25 mg/m² per day (no maximum dose defined in the source); the most frequent related events were decreased neutrophils (12.2%), increased insulin (10.2%) and stomatitis (10.2%) [102]. In two children with PROS (CLOVES and FIL with hemimegalencephaly), miransertib was discontinued for lack of sustained response [5, 110]. The extension NCT04980872 remains active, not recruiting, and the phase 2 study in Proteus syndrome (NCT04316546; NHGRI, n=38) has a primary completion date of 25 June 2026 [102]. In mice, prenatal miransertib rescued the lethality of a Proteus syndrome model, a preclinical finding [111]. None of these drugs is authorised for PROS [6].

7.12. Developments in the last twelve months

Other alpelisib studies are recruiting or active: EPIK-L1 (NCT05948943; lymphatic malformations, phase 2/3 with a randomised placebo-controlled stage and an open-label arm for 0–5 years), SESAM (NCT05577754; MCAP, 2–40 years, Vineland II scale endpoint at 24 months), TARGET-VM (NCT05983159; alpelisib in low-flow malformations and mirdametinib in high-flow ones) and VATCH (NCT07543822; TIE2/PIK3CA pathway anomalies, 2–30 years) [118–121]. The selective PI3Kα inhibitor CYH33 is in a phase I/II study in China (NCT06975618) [122]. Topical VT30 in venous and lymphatic malformations with a PIK3CA or TEK variant (NCT04409145) was terminated without completing part 2 [123]. Searches in Europe PMC found no peer-reviewed journal publication of EPIK-P2; the available results are those of the European assessment report and the trial registry [21, 99].

7.13. Agents to avoid and special situations

In Proteus syndrome, the sources recommend avoiding procoagulant drugs or those that increase the risk of DVT and growth-promoting drugs (androgenic steroids, GH), and the PROS consensus adopts a cautious position on GH (defer until after 2 years of age, because of a theoretical risk of tumorigenesis) [3, 34]. In women with a venous malformation and raised D-dimers who need oral contraception, the VASCERN pathway prefers the progestogen-only pill [85]. Patients with CLOVES and extensive venous malformations should have a haematological assessment and a thromboprophylaxis plan before any surgery, sclerotherapy or immobilisation, and assessment for thrombosis and coagulopathy after each intervention [1, 3]. MRI in young children requires sedation, and patients with head and neck involvement should have a sleep study, information relevant to anaesthetic planning [3, 5]. Pregnancy and lactation are dealt with in section 8.

Transition to adulthood is difficult because of the lack of a case manager equivalent to the paediatrician experienced in rare diseases, and primary care does not have the capacity to manage the disease alone [5]. Neuropsychological reassessment at transitions (puberty, secondary school, move to adult services) and integration with school and local services form part of the plan [3, 5].

The PNDS devotes a specific consultation to disclosure of the diagnosis, carried out by the specialist who suspected it or who ordered the test, explaining the characteristics of the disease, follow-up, its sporadic nature and genetic counselling, providing contact details of patient organisations and offering psychological support; this is followed by a letter to the corresponding physicians and, a few weeks later, a further consultation, possibly in a day hospital, to go over the information again, introduce the team, carry out the initial assessment and designate a referring physician [23]. Psychological support for the patient, siblings and carers addresses stress, pain, chronic inflammation, emotional regulation, sleep, school integration, the gaze of others and, later, employment and parenthood plans, with coping strategies that may be integrated into therapeutic education programmes [23]. Therapeutic education focuses on the progressive nature of the disease, complications, the limits and risk of recurrence of treatments, the use of anticoagulants, analgesics and antibiotic prophylaxis, adaptation of daily life and, in particular, recognition of the signs of DVT or PE, which require urgent consultation [23]. The PNDS does not include an emergency card and refers to the KTS emergency and anaesthesia guidelines published by Orphanet [23].

In rehabilitation, the PNDS indicates dental and orthodontic care in facial hypertrophy; occupational therapy in macrodactyly and involvement of the extremities (technical aids, also at school, and use of a prosthesis after amputation); podiatry for limb length discrepancy (insoles or orthopaedic footwear); orthotics and prosthetics (brace, prosthesis, technical aids in focal overgrowth); physiotherapy for scoliosis, pain, prevention of contractures and lymphatic drainage; speech therapy in hemifacial hypertrophy with articulation or swallowing disorders and in brain involvement; and psychomotor therapy in forms with brain involvement [23]. In France, the referring physician or family doctor completes the care protocol for recognition as an off-list long-term condition (ALD), sometimes from birth, and the application to the departmental centre for people with disabilities (MDPH) gives access to benefits and compensation arrangements; at school, an individualised reception project, a personalised schooling plan and the support of assistants for pupils with disabilities can be used [23]. The PNDS asks for transition to adult services to be organised at the end of adolescence, to avoid interruption of follow-up [23].

7.14. Guideline recommendations and divergences

Sources: [1–3, 5, 18–20, 23, 27, 65, 67, 68, 85, 124].

7.15. French national protocol (PNDS 2020) and divergences

The HAS PNDS for CLOVES and KTS without brain involvement, drawn up by the Dijon reference centres (developmental anomalies; rare dermatological diseases) and the Lyon competence centre for rare vascular diseases, coincides with the international consensus on multidisciplinary organisation, the requirement for affected tissue for testing and caution regarding debulking surgery, but diverges on several operational points [23].

Sources: [1–3, 5, 18, 19, 23, 47, 60, 62, 65, 68, 70, 85, 86, 124].

8. Reproductive Options and Family Counselling

8.1. Mechanism of occurrence and recurrence risks

PROS is not known to be an inherited disease: most variants are somatic, arising after fertilisation in a cell of the multicellular embryo, and neither vertical transmission nor recurrence in siblings has been confirmed [1]. The parents of a child with somatic mosaicism have no distinctive manifestations and do not need testing [1].

No pregnancy carries zero risk, but empirical evidence indicates that the recurrence risk in siblings is not increased [1]. GenCC records MCAP as "autosomal dominant", a label that describes the effect of a single copy (gain of function) and should not be read as a transmission risk in mosaic disease [6]. Familial recurrence has not been described in KTS; in a review of 49 cases all were sporadic, and the family history reported by 6.8% of patients in the Brazilian cohort has no molecular confirmation [11, 59]. The historical hypothesis of "paradominant" inheritance of KTS has no current support [1, 43]. The PNDS explains postzygotic mosaicism at the time of suspicion and again after confirmation, mentions it in all cases of CLOVES and in most of KTS and considers that the recurrence risk for the couple is not, a priori, higher than that of the population [23]. For the absence of described transmission from affected parent to child it proposes three explanations: the variant may not be in the germline; transmission in the constitutional, non-mosaic state could be lethal early in pregnancy, with early miscarriage; and offspring are rare in severe forms [23].

8.2. Cascade testing, prenatal and preimplantation diagnosis

Cascade testing of relatives is not indicated in mosaic PROS [1]. Prenatal diagnosis and preimplantation genetic testing (PGT) are not usually indicated for relatives; they may be an option in the rare families in which the child has a constitutional variant, because of the theoretical risk of parental germline mosaicism, or for the offspring of a patient with a constitutional variant [1, 3]. Prenatal molecular testing may be considered in pregnancies with an ultrasound suspicion of PROS, bearing in mind that mosaicism limits its sensitivity [1, 3]. When the fetus has PROS, the pregnancy may be complicated by polyhydramnios, preterm delivery, difficult delivery due to megalencephaly and breech presentation, and the fetal medicine team should plan the delivery, with fetal MRI if necessary (grade B evidence recommendation) [3]. The French PNDS considers prenatal diagnosis not usually indicated in a subsequent pregnancy of the couple, but accepts it in the face of an insistent parental request and proposes a reference ultrasound scan in a multidisciplinary prenatal diagnosis centre to reassure the family [23]. In the pregnancy of a parent with CLOVES or KTS, prenatal diagnosis may be proposed, with ultrasound surveillance as an alternative given the absence of described vertical transmission; non-invasive prenatal diagnosis on circulating fetal DNA was not offered in France for rare gene indications at the date of the protocol [23].

8.3. Pregnancy in a woman with PROS or KTS

Pregnancy may worsen vascular malformations. In a 2006 review, there were only 13 published cases of KTS in pregnancy since 1989; in a series of four patients, complications were haemorrhage, disseminated intravascular coagulation, thromboembolic events and pain, with maternal and fetal risks proportional to severity, which justifies preconception counselling and systematic care at delivery and in the puerperium [125]. Vulvovaginal malformations with a bleeding risk in the third trimester may determine the mode of delivery, which depends on severity and obstetric experience [126]. In pregnant women with a venous malformation and raised D-dimers, the VASCERN pathway indicates considering LMWH [85]. The PNDS considers that women with vascular manifestations, especially of the KTS spectrum, have an increased risk of venous thromboembolism in pregnancy and the early puerperium and of postpartum haemorrhage; they should be informed and followed from the preconception period, and anticoagulant prophylaxis should be discussed in the obstetric plan of patients with KTS, especially if there is LIC [23]. Like VASCERN, it prefers progestogen-only oral contraception when the clinical picture carries a thromboembolic risk [23, 85].

Alpelisib should not be used in pregnancy, because of embryofetal toxicity in animals; pregnancy should be excluded before starting, and contraception (with an additional barrier method in the EU, if hormonal) continues until 1 week after the last dose, as does abstaining from breastfeeding [18, 19]. Three women with PROS who became pregnant after prolonged treatment with alpelisib, stopped during pregnancy, have been described: all three pregnancies had a favourable outcome, the disease progressed during gestation in all three and the malformations responded again on resuming the drug, without secondary resistance; the authors conclude, on the basis of three cases, that alpelisib does not appear to affect female fertility [127]. As for sirolimus, gonadal effects are usually small and reversible: sperm and sex hormone changes normalised after discontinuation in transplant recipients, menstrual changes and ovarian cysts that improve with dose reduction or discontinuation, dysmenorrhoea in <10% (grade I–II) in the European VASE trial, reversible azoospermia in most according to the US label, and four pregnancies (one paternal) in three patients after 2 years of sirolimus in VASE [108].

8.4. Content of counselling

Counselling should explain the postzygotic nature of the disease, the absence of an increased risk to siblings in the mosaic form, the rare possibility of a constitutional variant and its significance for offspring, the limits of a negative test and the absence of an established germline cancer predisposition (ClinGen refutation for breast cancer) [1, 3, 6]. The optimal time to discuss the risk is before pregnancy, and counselling should be offered to affected young adults [1]. In minors, testing has no predictive purpose, because it is performed on affected tissue to confirm the diagnosis and guide treatment [1, 3].

9. Special Considerations: Population Diversity and Epidemiology

9.1. Prevalence and what each figure measures

The prevalence of PROS is difficult to estimate because of variation in ascertainment and the breadth of the phenotype [1]. The only published population-based study, from Piedmont (Italy), identified 37 patients with a clinical diagnosis of PROS among 825,593 live births from 1998 to 2021, corresponding to 1:22,313 (0.45 per 10,000); molecular analysis was positive in 30 (81.0%), and the prevalence of molecularly confirmed PROS was 1:27,519 (0.36 per 10,000), with no deaths in the period [15, 16]. The figure measures birth prevalence in one region, from patients diagnosed at a regional reference centre, and probably underestimates mild isolated forms. The EMA Committee for Orphan Medicinal Products estimated, for maintenance of the orphan designation in 2026, about 1 in 10,000 in the EU (1.25 per 10,000 at the initial designation in 2021), a regulatory estimate that aggregates diverse sources [16]. Orphanet classifies MCAP and CLOVES as <1/1,000,000, with about 170 and 150 published cases respectively, and has no prevalence entry for aggregate PROS; GeneReviews mentions more than 200 published individuals with MCAP [1, 6]. Numbers of published cases measure the literature, not population frequency. The French PNDS considers the exact prevalence unknown and estimates Proteus syndrome to be about 100 times rarer than CLOVES, without stating the basis for the calculation [23].

For KTS there is no validated population estimate in the sources consulted. A 2004 study used a prevalence of 1 in 47,313 as a comparator, and a Brazilian textbook from 2021 gives an incidence of 1:27,500 newborns and about 1000 cases described up to 2008, without an explicit primary source and with the joint designation of KTS and Parkes Weber syndrome [43, 67]. The textbook indicates no racial or geographical predisposition [43]. An analysis from the Spanish Collaborative Study of Congenital Malformations found increased parental age and number of pregnancies in consecutive KTS cases [11].

9.2. Data by region

EPIK-P1 recruited patients from France, Spain, the USA, Ireland and Australia, and EPIK-P2 screened 231 patients in 35 centres in 12 countries [18, 21]. The sources consulted describe no founder variants or differences in frequency between populations, which is expected in a disease of sporadic postzygotic mutations; nor do they describe ethnic differences in presentation.

9.3. Portugal and Brazil

The sources consulted contain no epidemiological data from Portugal; the Brazilian reference chapter cites a Portuguese case of KTS with gastrointestinal involvement published in 2009 [43]. Portugal is covered by the European conditional authorisation of Vijoice®, and the sources consulted give no information on its marketing or reimbursement [19]. In Brazil, the Santa Casa de São Paulo cohort (section 3.4) and the chapter of the Brazilian textbook of genetic syndromes use the designation "Klippel-Trenaunay-Weber", which ISSVA considers incorrect [26, 43, 59]. A Brazilian case of CLOVES published in 2016 in the Anais Brasileiros de Dermatologia was retracted in 2026 for legal reasons and should not be used as a reference [128]. No registration of Vijoice® with ANVISA was found in a search, which does not prove that none exists.

9.4. Special populations

Children under 2 years are outside the approved indications for alpelisib; data at this age are limited to reports of compassionate use with reduced doses, such as those in section 10 [18, 19, 47]. Adults are a relevant proportion of patients (31.6% in EPIK-P1; median age 26 years in a US observational study), and radiological progression is frequent in adulthood [19, 69, 117]. There are no patients aged 65 or over in the alpelisib studies [18]. Patients with uncontrolled type 1 or type 2 diabetes were excluded from EPIK-P2, and the safety of alpelisib has not been established in these patients [18, 21]. Pregnant women are covered in section 8.3.

9.5. Reference networks and patient organisations

Sources: [1, 3, 5, 22, 23, 44]. The M-CM Network, M-CM UK and AMCME España promoted the 2019 international consensus meeting [3]. The VASCERN page consulted does not publish a specific pathway for PROS or overgrowth, although the venous malformations pathway refers to an overgrowth pathway [22, 85]. In France, the PNDS is based on the AnDDI-Rares, FIMARAD and FAVA-Multi networks and also includes the centres for constitutional bone diseases; follow-up is usually coordinated by the geneticist or dermatologist of the reference or competence centre, in liaison with the paediatrician or family doctor, and referral to patient organisations is systematically proposed, with the patient or parents deciding whether to contact them [23].

10. Illustrative Clinical Case

10.1. Patient 1: CLOVES phenotype with extensive lymphatic-venous malformations

Morin and colleagues described, at the Necker hospital (Paris), two infants treated with alpelisib on a compassionate use basis authorised by the French medicines agency (ANSM) between July 2020 and August 2021 [47]. The first patient, a girl, had PROS with a CLOVES phenotype with mixed lymphatic and venous malformations of the retroperitoneum, pelvis and right lower limb, asymmetric overgrowth of the right leg and foot and bilateral macrodactyly of the toes and of the 2nd to 4th fingers of the right hand [47]. A skin biopsy of the right limb, on day 4 of life, identified by targeted panel the variant NM_006218.4:c.1349_1366del, p.(His450_Leu455del), an in-frame deletion with a VAF of 3% [7, 47]. In the first 6 months she had four episodes of cellulitis with septic shock and a femoral DVT; at 6 months she started prophylactic warfarin and phenoxymethylpenicillin, with a further episode of cellulitis [47]. MRI showed diffuse subcutaneous and intramuscular venous and lymphatic malformations of the right limb, with pelvic and retroperitoneal extension, inaccessible to surgery or interventional radiology; the child could not stand, had moderate non-regenerative anaemia (chronic inflammation, infections, local bleeding) and poor growth with low IGF1 [47].

At 9 months (8 months according to the article's abstract) she started alpelisib 25 mg per day [47]. The capillary malformation faded and the volume of the leg and of the malformations decreased; after 12 months of treatment the leg was less infiltrated, the foot more flexible and the child stood and walked with support, with no new infections; phenoxymethylpenicillin was stopped at 3 months and warfarin at 11 months [47]. The volume of the lymphatic malformations of the leg on MRI went from 837.4 cm³ to 454.3 cm³ at 6 months (−45.7%) and 321.9 cm³ at 12 months (−61.5%); the macrodactyly of the hand progressively decreased, growth recovered, IGF1 normalised and haemoglobin rose, without change in HbA1c, cholesterol or triglycerides [47]. Figure 1 of the article shows photographs of the pelvis, leg and hand before and after treatment, coronal STIR-weighted MRI, growth curves, IGF1, haemoglobin and reticulocytes and HbA1c and lipids: https://pmc.ncbi.nlm.nih.gov/articles/PMC8932545/figure/fig1/ [47].

10.2. Patient 2: MCAP phenotype with hemimegalencephaly

The second patient, a boy, had PROS with an MCAP phenotype with right hemimegalencephaly, asymmetric overgrowth of the right buttock, limb and foot, diffuse superficial capillary malformations and mild hypertrophy of the right hemiface [47]. A skin biopsy of the capillary malformation of the left leg, on day 18, identified NM_006218.4:c.3132T>A, p.(Asn1044Lys), with a VAF of 14.8% [7, 47]. At 2 months he developed West syndrome (flexion spasms, left hemiparesis); MRI showed an enlarged right hemisphere, thickened cortex suggestive of pachygyria and developmental venous anomalies, EEG showed right temporoparietal fast rhythms, and there was anaemia and hypercholesterolaemia; the spasms ceased with vigabatrin and corticosteroids [47]. At 8 months, with delayed milestones and global hypotonia, he started alpelisib 25 mg per day [47]. There was no recurrence of the spasms; psychomotor development normalised, although the authors stress that it is difficult to separate natural progress from the drug's effect; vigabatrin was replaced by sodium valproate, the capillary malformation faded, tone improved, the child acquired walking and HC showed a moderate inflection; there was transient hypertriglyceridaemia at month 3, HbA1c remained stable and brain MRIs at 3 and 12 months showed no anatomical change [47]. Figure 2 of the article shows the overgrowth of the right limb and the malformations of the left leg before and after, brain MRI with an arterial spin labelling sequence, growth, HC, IGF1, haemoglobin and metabolic parameters: https://pmc.ncbi.nlm.nih.gov/articles/PMC8932545/figure/fig2/ [47].

10.3. Pharmacokinetics, monitoring and context

With 25 mg per day, the steady-state maximum concentration (day 84) was 543 ng/mL and 835 ng/mL, similar to that of oncology adults treated with 60–90 mg and much lower than that obtained with 300 mg (about 3000 ng/mL), with about 4-fold accumulation, suggesting lower clearance and a longer half-life in infants [47]. Monitoring included blood glucose before each meal during the first week and, at 6 and 12 months, full blood count, C-reactive protein, D-dimers, fibrinogen, HbA1c, lipids, liver and renal function tests, creatine kinase, amylase, lipase, lactate dehydrogenase, IGF1, uric acid and MRI [47].

The two cases illustrate the severity PROS can reach in the first year (sepsis, thrombosis, early epilepsy, growth failure), the usefulness of early skin biopsy with detection of a VAF of 3% and of variants outside the hotspots, and the clinical and volumetric response of lymphatic and venous malformations to PI3Kα inhibition. The management described does not correspond to current practice: treatment was given below 2 years of age, an age outside the indications approved by the FDA and the EU, and with an unlabelled 25 mg dose, under compassionate use [18, 19, 47]. The authors acknowledge the selection bias and the number of two patients [47].

11. Prognosis and Long-Term Follow-up

11.1. Prognosis

Prognosis depends mainly on the extent of the malformations and on central nervous system involvement. Significant neurological involvement (DMEG, HMEG) is associated with an unfavourable prognosis, and in MCAP the degree of ID relates to seizures, cortical dysplasia and hydrocephalus [1]. Complex lymphatic anomalies, especially close to vital structures of the anterior head and neck, may have an aggressive course [1]. The Committee for Orphan Medicinal Products describes the condition as life-threatening and chronically debilitating, with limitation of walking and swallowing, renal and heart failure, pain, infections, neurodevelopmental delay, seizures, thromboembolism, pulmonary hypertension and bleeding [16]. Without treatment, 83.3% of patients in a French series had radiological progression, at a median rate of 7.2% per year, also in adulthood [69]. The cancer risk is low: 2.2% cancers in the Dijon cohort, with a cumulative probability of 5.6% at 45 years (95% CI 1.35–21.8%), and Wilms tumour in 1.4–3.3% of patients with a genetic diagnosis, concentrated in the first years and in CLOVES [1, 65, 68]. Quality of life is reduced by pain and loss of physical function, persistently over 12 months in an observational study [61, 117]. In the clinical description of the PNDS, which predates the 2026 radiological study, postnatal progression of CLOVES is usually moderate, with severe and progressive forms in some patients, and the course of the lesions is poorly predictable [23].

KTS usually has a good prognosis with conservative treatment; the most common complications are skin ulcers and infections, and serious ones include PE, thrombosis, haemothorax and heart failure, which may be fatal [25, 43]. In a Dutch cohort, 17% had had DVT or PE and 4.2% had chronic PE [60]. On alpelisib, the overall clinical response at 36 months was considered improved in 67.7% of children and 55.6% of adults in EPIK-P3, with stabilisation of limb asymmetry and hypertrophy in all those assessed, in a selected population [19, 21]. Data on reproductive and developmental outcomes in adults are limited [1].

11.2. Surveillance

Wilms tumour surveillance is the point of greatest divergence. GeneReviews proposes considering renal ultrasound every 3 months until 8 years and classifies the measure as controversial, noting that in the USA screening is often performed when the risk is ≥3% [1]. The 2015 criteria suggested ultrasound every 3–4 months until 8 years by analogy with Beckwith-Wiedemann syndrome, based on one case of Wilms in CLOVES and nephrogenic rests in another patient, and the Boston group proposed considering quarterly ultrasound until 7 years in CLOVES, with greater benefit before 3 years [2, 65]. The North American recommendation of the American Association for Cancer Research (AACR) reserves screening for syndromes with a risk ≥1% (renal ultrasound every 3 months until the 7th birthday) and does not recommend it in PROS, whereas it does recommend it in isolated hemihypertrophy, with a risk of 3–4% [124]. The international consensus and the French cohort find no data justifying routine periodic surveillance, and the Italian consensus describes both practices without consensus, noting that the doubling time of Wilms tumour, about 30 days (17–40), makes long intervals of little use [3, 5, 68]. The French PNDS also does not recommend surveillance, because the risk of Wilms tumour is below 5% in all studies, the threshold below which the 2006 British recommendations do not propose screening [23, 129]. In KTS, the absence of cases in 115 patients and of KTS among 8614 Wilms tumours underpins the absence of screening [67]. In the United Kingdom, consensus Wilms screening (ultrasound every 3–4 months until 7 years) applies to the high-risk epigenotypes of Beckwith-Wiedemann syndrome and to isolated hemihypertrophy [44, 129].

12. Summary and Final Considerations

The PIK3CA-related overgrowth spectrum brings together disorders previously described as separate entities, from KTS in 1900 to MCAP and CLOVES in 1997–2009, under a common cause: activating p110α variants arising after fertilisation, present only in the cell lineages that form the affected tissues. The phenotype depends on the timing of the mutation, the tissues that inherit it and the activating strength of the variant; strongly activating hotspot variants cause severe focal overgrowth at low-level mosaicism, and less activating ones are associated with the brain overgrowth of MCAP. The disease is not inherited in the mosaic form, the risk to siblings is that of the population and the very rare constitutional variant confers a 50% risk to offspring.

Diagnosis requires uncultured affected tissue and very high-depth sequencing of the whole gene, with a detection threshold of 1–5%, and a negative result, expected in 15–60% of cases, does not exclude the clinical diagnosis. Blood has a place as a first step only in MCAP. The main differential is Proteus syndrome, with postnatal onset, rapid progression, cerebriform connective tissue naevus and distorted bony overgrowth; this is followed by PTEN hamartoma tumour syndrome, high-flow Parkes Weber syndrome and MPPH. ISSVA discourages the term "Klippel-Trenaunay-Weber" and considers KTS a genomically non-uniform clinical diagnosis.

Management is multidisciplinary and rests on neurological surveillance of patients with brain involvement (MRI every 6 months until 2 years and annually until 8 years), haematological assessment and thromboprophylaxis before surgery or sclerotherapy, orthopaedic correction of limb discrepancy from 2 cm, endocrine screening of patients with brain involvement and an individualised decision on Wilms tumour surveillance, a point on which recommendations diverge. Alpelisib (Vijoice®) is the only authorised drug: FDA accelerated approval in 2022 and European conditional authorisation on 15 July 2026, based on a retrospective compassionate use study, after a first application withdrawn in 2023 and despite the placebo-controlled EPIK-P2 not meeting its primary endpoint; the mean effect on lesion volume was small and continued authorisation depends on EPIK-P4. The French 2020 national protocol for CLOVES and KTS adds a stepwise approach to pain, infection and anticoagulation centred on LMWH, class III compression, systematic postoperative prophylaxis with LMWH in extensive vascular malformations and clinical examination at least annually, and does not recommend Wilms tumour surveillance. Hyperglycaemia, diarrhoea, stomatitis, rash and hypersensitivity are the adverse effects to monitor, and the long-term effects on children's growth are unknown. Sirolimus produces modest volume reductions with frequent toxicity, taselisib and miransertib have not shown sufficient benefit, and selective inhibitors of mutant PI3Kα (zovegalisib, serabelisib, CYH33) are in trials whose known results come from press releases or the media. The natural history, with radiological progression in most untreated patients, is the reference for interpreting these results.

13. References

1. Mirzaa G, Graham JM Jr, Keppler-Noreuil K. PIK3CA-Related Overgrowth Spectrum. 2013 Aug 15 [updated 2021 Dec 23; reviewed 2023 Apr 6]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews®. Seattle (WA): University of Washington, Seattle; 1993–2026. NBK153722. https://www.ncbi.nlm.nih.gov/books/NBK153722/
2. Keppler-Noreuil KM, Rios JJ, Parker VE, Semple RK, Lindhurst MJ, Sapp JC, et al. PIK3CA-related overgrowth spectrum (PROS): diagnostic and testing eligibility criteria, differential diagnosis, and evaluation. Am J Med Genet A. 2015;167A:287-95. doi:10.1002/ajmg.a.36836. PMID: 25557259. PMC4480633.
3. Douzgou S, Rawson M, Baselga E, Danielpour M, Faivre L, Kashanian A, et al. A standard of care for individuals with PIK3CA-related disorders: An international expert consensus statement. Clin Genet. 2022;101:32-47. doi:10.1111/cge.14027. PMID: 34240408. PMC8664971.
4. Canaud G, Hammill AM, Adams D, Vikkula M, Keppler-Noreuil KM. A review of mechanisms of disease across PIK3CA-related disorders with vascular manifestations. Orphanet J Rare Dis. 2021;16:306. doi:10.1186/s13023-021-01929-8. PMID: 34238334. PMC8268514.
5. Gazzin A, Leoni C, Viscogliosi G, Borgini F, Perri L, Iacoviello M, et al. Work-Up and Treatment Strategies for Individuals with PIK3CA-Related Disorders: A Consensus of Experts from the Scientific Committee of the Italian Macrodactyly and PROS Association. Genes (Basel). 2023;14. doi:10.3390/genes14122134. PMID: 38136956. PMC10742781.
6. GeneGuidance. PIK3CA: clinical gene curation (identifiers, ClinGen, GenCC, Orphanet, openFDA labels). Local database, version of 26 Sep 2026. Accessed 17 Oct 2026.
7. Freeman PJ, Hart RK, Gretton LJ, Brookes AJ, Dalgleish R. VariantValidator: accurate validation, mapping, and formatting of sequence variation descriptions. Hum Mutat. 2018;39(1):61-8. doi:10.1002/humu.23348. PMID: 28967166. Accessed 2026-10-17. https://variantvalidator.org
8. Mirzaa G, Timms AE, Conti V, Boyle EA, Girisha KM, Martin B, et al. PIK3CA-associated developmental disorders exhibit distinct classes of mutations with variable expression and tissue distribution. JCI Insight. 2016;1. doi:10.1172/jci.insight.87623. PMID: 27631024. PMC5019182.
9. Orphanet. PIK3CA-related overgrowth spectrum disorder (ORPHA:530313) and associated entities (ORPHA:728584, 140944, 60040, 90308, 168984, 276280, 314662, 583097, 699683, 295239, 295243, 99802, 329324). Orphadata, version of 2026. https://www.orpha.net/en/disease/detail/530313. Accessed 17 Oct 2026.
10. Online Mendelian Inheritance in Man (OMIM). *171834 Phosphatidylinositol 3-kinase, catalytic, alpha; PIK3CA. Baltimore (MD): Johns Hopkins University. https://www.omim.org/entry/171834. Accessed 17 Oct 2026.
11. Online Mendelian Inheritance in Man (OMIM). %149000 Klippel-Trenaunay-Weber syndrome. Baltimore (MD): Johns Hopkins University. https://www.omim.org/entry/149000. Accessed 17 Oct 2026.
12. Online Mendelian Inheritance in Man (OMIM). #602501 Megalencephaly-capillary malformation-polymicrogyria syndrome; MCAP. Baltimore (MD): Johns Hopkins University. https://www.omim.org/entry/602501. Accessed 17 Oct 2026.
13. Online Mendelian Inheritance in Man (OMIM). #612918 Congenital lipomatous overgrowth, vascular malformations, and epidermal nevi (CLOVE syndrome). Baltimore (MD): Johns Hopkins University. https://www.omim.org/entry/612918. Accessed 17 Oct 2026.
14. Online Mendelian Inheritance in Man (OMIM). #613089 Capillary malformation of the lower lip, lymphatic malformation of face and neck, asymmetry of face and limbs, and partial/generalized overgrowth; CLAPO. Baltimore (MD): Johns Hopkins University. https://www.omim.org/entry/613089. Accessed 17 Oct 2026.
15. Reynolds G, Cardaropoli S, Carli D, Luca M, Gazzin A, Coppo P, et al. Epidemiology of the disorders of the Pik3ca-related overgrowth spectrum (Pros). Eur J Hum Genet. 2023;31:1333-1336. doi:10.1038/s41431-023-01414-9. PMID: 37365400. PMC10620148.
16. European Medicines Agency, Committee for Orphan Medicinal Products. Vijoice: orphan maintenance assessment report — initial authorisation. EMADOC-1700519818-3188437. 2026. https://www.ema.europa.eu/en/documents/orphan-maintenance-report/vijoice-orphan-maintenance-assessment-report-initial-authorisation_en.pdf
17. Keppler-Noreuil KM, Sapp JC, Lindhurst MJ, Parker VE, Blumhorst C, Darling T, et al. Clinical delineation and natural history of the PIK3CA-related overgrowth spectrum. Am J Med Genet A. 2014;164A:1713-33. doi:10.1002/ajmg.a.36552. PMID: 24782230. PMC4320693.
18. Novartis Pharmaceuticals Corporation. VIJOICE (alpelisib) tablets, for oral use; VIJOICE (alpelisib) oral granules. Prescribing information. Revised 7/2025 (SPL set ID 638069a4-aee0-46c9-9e21-54ad449c163c, version 10). Drugs@FDA NDA 215039 (tablets; accelerated approval 05/04/2022) and NDA 218466 (granules; 24/04/2024). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=638069a4-aee0-46c9-9e21-54ad449c163c
19. European Medicines Agency. Vijoice (alpelisib): EPAR — product information (summary of product characteristics). EMEA/H/C/006539. Conditional marketing authorisation 15/07/2026; first published 26/08/2026. https://www.ema.europa.eu/en/medicines/human/EPAR/vijoice
20. Revencu N, Eijkelenboom A, Bracquemart C, Alhopuro P, Armstrong J, Baselga E, et al. Assessment of gene-disease associations and recommendations for genetic testing for somatic variants in vascular anomalies by VASCERN-VASCA. Orphanet J Rare Dis. 2024;19(1):213. doi:10.1186/s13023-024-03196-9. PMID: 38778413.
21. European Medicines Agency, Committee for Medicinal Products for Human Use. Vijoice: EPAR — public assessment report. EMADOC-1829012207-22240. Amsterdam: EMA; 2026. https://www.ema.europa.eu/en/documents/assessment-report/vijoice-epar-public-assessment-report_en.pdf
22. VASCERN. Vascular Anomalies (VASCA-WG). https://vascern.eu/groupe/vascular-anomalies/
23. Haute Autorité de Santé. Protocole National de Diagnostic et de Soins (PNDS): Syndromes hypertrophiques liés au gène PIK3CA (PROS) sans atteinte cérébrale — Les syndromes CLOVES et de Klippel-Trenaunay. Centre de référence Anomalies du développement et syndromes malformatifs de l'interrégion Est (filière AnDDI-Rares), Centre de référence Maladies dermatologiques rares interrégion Est (filière FIMARAD) and Centre de compétence Maladies vasculaires rares de Lyon (filière FAVA-Multi); coordination Olivier-Faivre L, Vabres P, Guibaud L. Saint-Denis La Plaine: HAS; text of November 2020 (published 22 Dec 2020). Available from: https://www.has-sante.fr/jcms/p_3226371. Accessed 6 Nov 2026.
24. Klippel M, Trenaunay P. Du naevus variqueux ostéohypertrophique. Arch Gen Med. 1900;185:641. Citado em: Jones KL, Jones MC, del Campo M. Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia: Elsevier; 2022. p. 726.
25. Jones KL, Jones MC, del Campo M. Klippel-Trenaunay syndrome. In: Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia: Elsevier; 2022. p. 724–727.
26. International Society for the Study of Vascular Anomalies. ISSVA Classification for Vascular Anomalies and Glossary (2025). Reviewed at the ISSVA World Congress, Madrid, May 2024; glossary updated March 2025. https://www.issva.org/classification
27. Jacob AG, Driscoll DJ, Shaughnessy WJ, Stanson AW, Clay RP, Gloviczki P. Klippel-Trénaunay syndrome: spectrum and management. Mayo Clin Proc. 1998;73:28-36. doi:10.1016/S0025-6196(11)63615-X. PMID: 9443675.
28. Clayton-Smith J, Kerr B, Brunner H, Tranebjaerg L, Magee A, Hennekam RC, et al. Macrocephaly with cutis marmorata, haemangioma and syndactyly--a distinctive overgrowth syndrome. Clin Dysmorphol. 1997;6:291-302. doi:10.1097/00019605-199710000-00001. PMID: 9354837.
29. Moore CA, Toriello HV, Abuelo DN, Bull MJ, Curry CJ, Hall BD, et al. Macrocephaly-cutis marmorata telangiectatica congenita: a distinct disorder with developmental delay and connective tissue abnormalities. Am J Med Genet. 1997;70:67-73. PMID: 9129744.
30. Jones KL, Jones MC, del Campo M. Megalencephaly-capillary malformation-polydactyly syndrome. In: Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia: Elsevier; 2022. p. 732–735.
31. Gripp KW, Hopkins E, Vinkler C, et al. Significant overlap and possible identity of macrocephaly capillary malformation and megalencephaly polymicrogyria-polydactyly hydrocephalus syndromes. Am J Med Genet A. 2009;149A:868-76. PMID: 19353582. https://pubmed.ncbi.nlm.nih.gov/19353582/
32. Sapp JC, Turner JT, van de Kamp JM, van Dijk FS, Lowry RB, Biesecker LG. Newly delineated syndrome of congenital lipomatous overgrowth, vascular malformations, and epidermal nevi (CLOVE syndrome) in seven patients. Am J Med Genet A. 2007;143A:2944-58. doi:10.1002/ajmg.a.32023. PMID: 17963221.
33. Alomari AI. Characterization of a distinct syndrome that associates complex truncal overgrowth, vascular, and acral anomalies: a descriptive study of 18 cases of CLOVES syndrome. Clin Dysmorphol. 2009;18:1-7. doi:10.1097/MCD.0b013e328317a716. PMID: 19011570.
34. Biesecker LG, Sapp JC. Proteus Syndrome. 2012 Aug 9 [updated 2023 May 25]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews®. Seattle (WA): University of Washington, Seattle; 1993–2026. NBK99495. https://www.ncbi.nlm.nih.gov/books/NBK99495/
35. Lindhurst MJ, Sapp JC, Teer JK, Johnston JJ, Finn EM, Peters K, et al. A mosaic activating mutation in AKT1 associated with the Proteus syndrome. N Engl J Med. 2011;365:611-9. doi:10.1056/NEJMoa1104017. PMID: 21793738. PMC3170413.
36. Kurek KC, Luks VL, Ayturk UM, Alomari AI, Fishman SJ, Spencer SA, et al. Somatic mosaic activating mutations in PIK3CA cause CLOVES syndrome. Am J Hum Genet. 2012;90:1108-15. doi:10.1016/j.ajhg.2012.05.006. PMID: 22658544. PMC3370283.
37. Lindhurst MJ, Parker VE, Payne F, Sapp JC, Rudge S, Harris J, et al. Mosaic overgrowth with fibroadipose hyperplasia is caused by somatic activating mutations in PIK3CA. Nat Genet. 2012;44:928-33. doi:10.1038/ng.2332. PMID: 22729222. PMC3461408.
38. Rivière JB, Mirzaa GM, O'Roak BJ, Beddaoui M, Alcantara D, Conway RL, et al. De novo germline and postzygotic mutations in AKT3, PIK3R2 and PIK3CA cause a spectrum of related megalencephaly syndromes. Nat Genet. 2012;44:934-40. doi:10.1038/ng.2331. PMID: 22729224. PMC3408813.
39. Lee JH, Huynh M, Silhavy JL, Kim S, Dixon-Salazar T, Heiberg A, et al. De novo somatic mutations in components of the PI3K-AKT3-mTOR pathway cause hemimegalencephaly. Nat Genet. 2012;44:941-5. doi:10.1038/ng.2329. PMID: 22729223. PMC4417942.
40. Luks VL, Kamitaki N, Vivero MP, Uller W, Rab R, Bovée JV, et al. Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA. J Pediatr. 2015;166:1048-54.e1-5. doi:10.1016/j.jpeds.2014.12.069. PMID: 25681199. PMC4498659.
41. National Center for Biotechnology Information. ClinVar; VCV000402345. NM_018046.5(AGGF1):c.397G>A (p.Glu133Lys). Bethesda (MD): National Library of Medicine. https://www.ncbi.nlm.nih.gov/clinvar/variation/402345/ (accessed 2026-11-01).
42. Vahidnezhad H, Youssefian L, Uitto J. Klippel-Trenaunay syndrome belongs to the PIK3CA-related overgrowth spectrum (PROS). Exp Dermatol. 2016;25:17-9. doi:10.1111/exd.12826. PMID: 26268729.
43. Moura LEB, Queiroz SF, Ribeiro EM. Síndrome de Klippel-Trenaunay-Weber (SKTW). In: Ribeiro EM, coord. Síndromes Genéticas: Reconhecer para Tratar. Fortaleza: EdUnichristus; 2021. p. 202–205.
44. Firth HV, Hurst JA. Overgrowth. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 272–275.
45. Saudubray JM, Baumgartner MR, García-Cazorla Á, Walter J, editors. Inborn Metabolic Diseases: Diagnosis and Treatment. 7th ed. Berlin: Springer; 2022. Chapter 6, Congenital Hyperinsulinism and Genetic Disorders of Insulin Resistance and Signalling, secções 6.1–6.4.
46. Firth HV, Hurst JA. Macrocephaly. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 224–227.
47. Morin G, Degrugillier-Chopinet C, Vincent M, Fraissenon A, Aubert H, Chapelle C, et al. Treatment of two infants with PIK3CA-related overgrowth spectrum by alpelisib. J Exp Med. 2022;219. doi:10.1084/jem.20212148. PMID: 35080595. PMC8932545.
48. Kuentz P, St-Onge J, Duffourd Y, Courcet JB, Carmignac V, Jouan T, et al. Molecular diagnosis of PIK3CA-related overgrowth spectrum (PROS) in 162 patients and recommendations for genetic testing. Genet Med. 2017;19:989-997. doi:10.1038/gim.2016.220. PMID: 28151489.
49. Online Mendelian Inheritance in Man (OMIM). #615108 Cowden syndrome 5; CWS5. Baltimore (MD): Johns Hopkins University. https://www.omim.org/entry/615108. Accessed 17 Oct 2026.
50. Saudubray JM, Baumgartner MR, García-Cazorla Á, Walter J, editors. Inborn Metabolic Diseases: Diagnosis and Treatment. 7th ed. Berlin: Springer; 2022. Chapter 35, section 35.5 Inborn Errors of Phosphoinositide Phosphorylation (Table 35.1).
51. Green TE, Garza D, Brown NJ, de Silva MG, Bennett MF, Tubb C, et al. Improving genetic diagnostic yield in a large cohort of children with rare vascular anomalies or PIK3CA-related overgrowth spectrum. Genet Med Open. 2024;2:100837. doi:10.1016/j.gimo.2023.100837. PMID: 39669602. PMC11613910.
52. Merkle S, Alharbi S, Pastura P, McDaniel CG, Le Cras TD. Sirolimus outperforms alpelisib in models of NRAS (Q61R) -driven vascular overgrowth. Blood Vessel Thromb Hemost. 2026;3:100192. doi:10.1016/j.bvth.2026.100192. PMID: 42621428. PMC13488051.
53. Conway RL, Pressman BD, Dobyns WB, et al. Neuroimaging findings in macrocephaly-capillary malformation: a longitudinal study of 17 patients. Am J Med Genet A. 2007;143A:2981-3008. PMID: 18000912. https://pubmed.ncbi.nlm.nih.gov/18000912/
54. Olivier-Faivre L, Thauvin C, Guibaud L, Bahi-Buisson N, coordinators. Protocole National de Diagnostic et de Soins (PNDS): Syndrome MCAP (Megalencephaly-Capillary malformation-Polymicrogyria). Saint-Denis: Haute Autorité de Santé; 2021 Sep. Available from: https://www.has-sante.fr/upload/docs/application/pdf/2021-10/pnds-mcap_sept_2021.pdf
55. Couto JA, Konczyk DJ, Vivero MP, et al. Somatic PIK3CA mutations are present in multiple tissues of facial infiltrating lipomatosis. Pediatr Res. 2017;82:850-4. PMID: 28665924. https://pubmed.ncbi.nlm.nih.gov/28665924/
56. Rodriguez-Laguna L, Agra N, Ibañez K, et al. Somatic activating mutations in PIK3CA cause generalized lymphatic anomaly. J Exp Med. 2019;216:407-18. PMID: 30591517. https://pubmed.ncbi.nlm.nih.gov/30591517/
57. Oduber CE, Young-Afat DA, van der Wal AC, van Steensel MA, Hennekam RC, van der Horst CM. The persistent embryonic vein in Klippel-Trenaunay syndrome. Vasc Med. 2013;18:185-91. doi:10.1177/1358863X13498463. PMID: 23966121.
58. Li D, Yang H, Li J, Tan X, Liu Z, Xia J, et al. A novel Doppler ultrasound approach for phenotypic assessment and follow-up of Klippel-Trénaunay syndrome: A retrospective multicenter study. Phlebology. 2026:2683555261490370. doi:10.1177/02683555261490370. PMID: 42759969.
59. Villela ALC, Guedes LGS, Paschoa VVA, David AB, Tenório TM, Lamego Junior HP, et al. Perfil epidemiológico de 58 portadores de síndrome de Klippel-Trénaunay-Weber acompanhados no Ambulatório da Santa Casa de São Paulo. J Vasc Bras. 2009;8(3):219-24. doi:10.1590/S1677-54492009000300006.
60. Douma RA, Oduber CE, Gerdes VE, van Delden OM, van Eck-Smit BL, Meijers JC, et al. Chronic pulmonary embolism in Klippel-Trenaunay syndrome. J Am Acad Dermatol. 2012;66:71-7. doi:10.1016/j.jaad.2010.12.002. PMID: 21571392.
61. Oduber CE, Khemlani K, Sillevis Smitt JH, Hennekam RC, van der Horst CM. Baseline Quality of Life in patients with Klippel-Trenaunay syndrome. J Plast Reconstr Aesthet Surg. 2010;63:603-9. doi:10.1016/j.bjps.2009.01.055. PMID: 19289309.
62. Parker VER, Keppler-Noreuil KM, Faivre L, Luu M, Oden NL, De Silva L, et al. Safety and efficacy of low-dose sirolimus in the PIK3CA-related overgrowth spectrum. Genet Med. 2019;21:1189-1198. doi:10.1038/s41436-018-0297-9. PMID: 30270358. PMC6752269.
63. Keppler-Noreuil KM, Lozier J, Oden N, et al. Thrombosis risk factors in PIK3CA-related overgrowth spectrum and Proteus syndrome. Am J Med Genet C Semin Med Genet. 2019;181:571-81. PMID: 31490637. https://pubmed.ncbi.nlm.nih.gov/31490637/
64. Leiter SM, Parker VER, Welters A, et al. Hypoinsulinaemic, hypoketotic hypoglycaemia due to mosaic genetic activation of PI3-kinase. Eur J Endocrinol. 2017;177:175-86. PMID: 28566443. https://pubmed.ncbi.nlm.nih.gov/28566443/
65. Peterman CM, Fevurly RD, Alomari AI, Trenor CC 3rd, Adams DM, Vadeboncoeur S, et al. Sonographic screening for Wilms tumor in children with CLOVES syndrome. Pediatr Blood Cancer. 2017;64. doi:10.1002/pbc.26684. PMID: 28627003.
66. Peterman CM, Vadeboncoeur S, Mulliken JB, Fishman SJ, Liang MG. Wilms tumor screening in diffuse capillary malformation with overgrowth and macrocephaly-capillary malformation: A retrospective study. J Am Acad Dermatol. 2017;77:874-878. doi:10.1016/j.jaad.2017.06.014. PMID: 28822558.
67. Greene AK, Kieran M, Burrows PE, Mulliken JB, Kasser J, Fishman SJ. Wilms tumor screening is unnecessary in Klippel-Trenaunay syndrome. Pediatrics. 2004;113:e326-9. doi:10.1542/peds.113.4.e326. PMID: 15060262.
68. Faivre L, Crépin JC, Réda M, Nambot S, Carmignac V, Abadie C, et al. Low risk of embryonic and other cancers in PIK3CA-related overgrowth spectrum: Impact on screening recommendations. Clin Genet. 2023;104:554-563. doi:10.1111/cge.14410. PMID: 37580112.
69. Fraissenon A, Morin G, Boddaert N, Loiselet K, Berteloot L, Guibaud L, et al. Radiological evaluation of the natural history of PIK3CA-related overgrowth spectrum (PROS). Eur J Radiol. 2026;204:113108. doi:10.1016/j.ejrad.2026.113108. PMID: 42520377.
70. Firth HV, Hurst JA. Hemihypertrophy and limb asymmetry. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 164–166.
71. Oduber CE, van der Horst CM, Hennekam RC. Klippel-Trenaunay syndrome: diagnostic criteria and hypothesis on etiology. Ann Plast Surg. 2008;60:217-23. doi:10.1097/SAP.0b013e318062abc1. PMID: 18216519.
72. Jones KL, Jones MC, del Campo M. Parkes Weber syndrome. In: Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia: Elsevier; 2022. p. 728–731.
73. Jones KL, Jones MC, del Campo M. Encephalocraniocutaneous lipomatosis. In: Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia: Elsevier; 2022. p. 740–741.
74. Firth HV, Hurst JA. Cowden syndrome (PTEN hamartoma tumour syndrome). In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 564–567.
75. Jones KL, Jones MC, del Campo M. Proteus syndrome. In: Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia: Elsevier; 2022. p. 736–739.
76. Sapp JC, Buser A, Burton-Akright J, Keppler-Noreuil KM, Biesecker LG. A dyadic genotype-phenotype approach to diagnostic criteria for Proteus syndrome. Am J Med Genet C Semin Med Genet. 2019;181(4):565-70. doi:10.1002/ajmg.c.31744. PMID: 31692258. https://pubmed.ncbi.nlm.nih.gov/31692258/
77. Biesecker LG, Happle R, Mulliken JB, et al. Proteus syndrome: diagnostic criteria, differential diagnosis, and patient evaluation. Am J Med Genet. 1999;84:389-95. PMID: 10360391. https://pubmed.ncbi.nlm.nih.gov/10360391/
78. Revencu N, Boon LM, Mendola A, et al. RASA1 mutations and associated phenotypes in 68 families with capillary malformation-arteriovenous malformation. Hum Mutat. 2013;34:1632-41. PMID: 24038909. https://pubmed.ncbi.nlm.nih.gov/24038909/
79. Eerola I, Boon LM, Mulliken JB, et al. Capillary malformation-arteriovenous malformation, a new clinical and genetic disorder caused by RASA1 mutations. Am J Hum Genet. 2003;73:1240-9. PMID: 14639529. https://pubmed.ncbi.nlm.nih.gov/14639529/
80. Firth HV, Hurst JA. Lissencephaly, polymicrogyria, and neuronal migration disorders. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 216–221.
81. Firth HV, Hurst JA. Lumps and bumps. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 222–223.
82. Firth HV, Hurst JA. Facial asymmetry. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 146–149.
83. Firth HV, Hurst JA. Oedema, generalized or puffy extremities. In: Oxford Desk Reference: Clinical Genetics and Genomics. 2nd ed. Oxford: Oxford University Press; 2017. p. 260–263.
84. Connell FC, Gordon K, Brice G, et al. The classification and diagnostic algorithm for primary lymphatic dysplasia: an update from 2010 to include molecular findings. Clin Genet. 2013;84:303-14. PMID: 23621851. https://pubmed.ncbi.nlm.nih.gov/23621851/
85. VASCERN Vascular Anomalies Working Group (VASCA-WG). Venous Malformation Patient Pathway. 29 Apr 2020. https://vascern.eu/app/uploads/2023/03/VASCA-Patient-Pathway-Venous-Malformations-20200429-2.pdf
86. Haute Autorité de Santé. Prise en charge des infections cutanées bactériennes courantes. Fiche de synthèse de la recommandation de bonne pratique. Saint-Denis La Plaine: HAS; February 2019. Available from: https://www.has-sante.fr/jcms/c_2911550/fr/prise-en-charge-des-infections-cutanees-bacteriennes-courantes. Accessed 6 Nov 2026.
87. Cardinal Health 107, LLC (sanofi-aventis U.S.). LOVENOX (enoxaparin sodium injection), for subcutaneous and intravenous use. Prescribing information. SPL set ID 3d263380-4f44-4fd8-aa2a-e69702ab258f (version of 27/04/2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3d263380-4f44-4fd8-aa2a-e69702ab258f
88. NuCare Pharmaceuticals, Inc. Ibuprofen oral suspension. Prescribing information. SPL set ID 141b7964-cce6-74e4-e063-6294a90af746 (version of 20/03/2024). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=141b7964-cce6-74e4-e063-6294a90af746
89. Mahmoud AA, Basta MGZ, Hagag MA. Early endovenous laser ablation with 1940-nm wavelength for symptomatic marginal veins in pediatric Klippel-Trenaunay syndrome: A 4-year retrospective cohort study on safety, limb hypertrophy, and quality of life. J Vasc Surg Venous Lymphat Disord. 2026:102614. doi:10.1016/j.jvsv.2026.102614. PMID: 42697435.
90. Haute Autorité de Santé. Protocole National de Diagnostic et de Soins (PNDS): Malformations lymphatiques kystiques. Filières de santé maladies rares FIMARAD, TETECOU et FAVAmulti. Saint-Denis La Plaine: HAS; 2021 Mar. Available from: https://www.has-sante.fr/jcms/p_3241227
91. Davis S, Ware MA, Zeiger J, et al. Growth hormone deficiency in megalencephaly-capillary malformation syndrome: an association with activating mutations in PIK3CA. Am J Med Genet A. 2020;182:162-8. PMID: 31729162. https://pubmed.ncbi.nlm.nih.gov/31729162/
92. Venot Q, Blanc T, Rabia SH, Berteloot L, Ladraa S, Duong JP, et al. Targeted therapy in patients with PIK3CA-related overgrowth syndrome. Nature. 2018;558:540-546. doi:10.1038/s41586-018-0217-9. PMID: 29899452. PMC7610773.
93. ESMO Handbook of Cancer Genomics. Breast cancer: genomics. Lugano: ESMO Press. p. 82-91.
94. Canaud G, Lopez Gutierrez JC, Irvine AD, Vabres P, Hansford JR, Ankrah N, et al. Alpelisib for treatment of patients with PIK3CA-related overgrowth spectrum (PROS). Genet Med. 2023;25:100969. doi:10.1016/j.gim.2023.100969. PMID: 37634128.
95. Deriouich M, Dompmartin A, Canaud G, L'Orphelin JM. Hyperglycemic hyperosmolar coma induced by alpelisib in PIK3CA-related overgrowth spectrum (PROS). Ann Dermatol Venereol. 2025;152:103354. doi:10.1016/j.annder.2025.103354. PMID: 40157139.
96. European Medicines Agency. Vijoice: withdrawal of application (questions and answers EMA/492147/2023, 10/11/2023; updated 14/03/2024). https://www.ema.europa.eu/en/medicines/human/EPAR/vijoice-w
97. European Medicines Agency, CHMP. Summary of opinion (initial authorisation): Vijoice, alpelisib. EMADOC-1829012207-50265. 21 May 2026. https://www.ema.europa.eu/en/documents/smop-initial/chmp-summary-positive-opinion-vijoice_en.pdf
98. European Medicines Agency, CHMP. Vijoice (alpelisib) EMEA/H/C/006539/0000: divergent position dated 21 May 2026. https://www.ema.europa.eu/en/documents/scientific-conclusion/vijoice-epar-divergent-position-chmp_en.pdf
99. ClinicalTrials.gov. NCT04589650 — Study assessing the efficacy, safety and PK of alpelisib (BYL719) in pediatric and adult patients with PIK3CA-related overgrowth spectrum (EPIK-P2). Novartis. Results posted in the registry on 10/02/2025. https://clinicaltrials.gov/study/NCT04589650
100. ClinicalTrials.gov. NCT04980833 — EPIK-P3, long-term safety and efficacy of alpelisib in PROS (CBYL719F12401). https://clinicaltrials.gov/study/NCT04980833
101. Luu M, Vabres P, Devilliers H, Loffroy R, Phan A, Martin L, et al. Safety and efficacy of low-dose PI3K inhibitor taselisib in adult patients with CLOVES and Klippel-Trenaunay syndrome (KTS): the TOTEM trial, a phase 1/2 multicenter, open-label, single-arm study. Genet Med. 2021;23:2433-2442. doi:10.1038/s41436-021-01290-y. PMID: 34385668. PMC8631579.
102. Eng W, Iacobas I, Perkins J, Zampino G, Leoni C, Buonuomo PS, et al. Safety findings from the phase 1/2 MOSAIC study of miransertib for patients with PIK3CA-related overgrowth spectrum or Proteus syndrome. Orphanet J Rare Dis. 2025;20:375. doi:10.1186/s13023-025-03831-z. PMID: 40713644. PMC12296598.
103. Relay Therapeutics, Inc. Form 8-K, Item 7.01/8.01, and Exhibit 99.1 (press release: initial clinical data from the Phase 2 ReInspire trial of zovegalisib in vascular anomalies). Filed 19 May 2026. https://www.sec.gov/Archives/edgar/data/1812364/000119312526229770/rlay-20260519.htm
104. Pharmaphorum. Kaken details the data behind its PI3K inhibitor filing. 22 Jul 2026. https://pharmaphorum.com/news/kaken-details-data-behind-its-pi3k-inhibitor-filing
105. Jiho (日刊薬業). 科研製薬、KP-001を承認申請 (application for authorisation of KP-001 for vascular malformations). 15 May 2026. https://nk.jiho.jp/article/302223
106. Singh S, Bradford D, Li X, Mishra-Kalyani PS, Shen YL, Wang L, et al. FDA Approval Summary: Alpelisib for PIK3CA-Related Overgrowth Spectrum. Clin Cancer Res. 2024;30:23-28. doi:10.1158/1078-0432.CCR-23-1270. PMID: 37624421. PMC10841299.
107. Zhu Z, Yuan SM. Advances in the Targeted Therapy for PIK3CA-Related Overgrowth Spectrum (PROS): From Molecular Mechanisms to Clinical Translation. Pediatr Blood Cancer. 2026:e70697. doi:10.1002/1545-5017.70697. PMID: 42747160.
108. VASCERN-VASCA. Consensus Statement: Sirolimus and Fertility. Version 1, 20 Dec 2023. https://vascern.eu/app/uploads/2023/12/VASCERN-VASCA-Statement-on-Sirolimus-and-Fertility.pdf
109. ClinicalTrials.gov. NCT02509468 — PERFORMUS, sirolimus in superficial slow-flow vascular malformations (CHU Tours). https://clinicaltrials.gov/study/NCT02509468
110. Forde K, Resta N, Ranieri C, Rea D, Kubassova O, Hinton M, et al. Clinical experience with the AKT1 inhibitor miransertib in two children with PIK3CA-related overgrowth syndrome. Orphanet J Rare Dis. 2021;16:109. doi:10.1186/s13023-021-01745-0. PMID: 33639990. PMC7913425.
111. Abdul Rahiman Sirajuddeen SR, Lindhurst MJ, Detels M, Laughner N, Johnston J, Brinster LR, et al. Rescue of Proteus syndrome lethality in mice with prenatal miransertib treatment. Genet Med. 2026:102732. doi:10.1016/j.gim.2026.102732. PMID: 42788321.
112. ClinicalTrials.gov. NCT06997588 — EPIK-P4 (CBYL719F12202). https://clinicaltrials.gov/study/NCT06997588
113. ClinicalTrials.gov. NCT07285005 — S-KY, KP-001 vs placebo in common VM, common LM, or KTS/CLOVES (Kaken Pharmaceutical). https://clinicaltrials.gov/study/NCT07285005
114. Pellegrino F, Reynolds G, Cardaropoli S, Luca M, Massuras S, Carli D, et al. Alpelisib in PIK3CA-Related Overgrowth Spectrum (PROS): A Systematic Review of Real-World Evidence in over 100 Patients. Cells. 2026;15. doi:10.3390/cells15090788. PMID: 42121892. PMC13162736.
115. Pithadia DJ, Heskel MJ, Shotayev A, Davda S, Durand R, Cooke D, et al. Alpelisib, a PI3Kα inhibitor, effectively treats vascular anomalies with diverse genotypes and phenotypes. Blood Vessel Thromb Hemost. 2026;3:100133. doi:10.1016/j.bvth.2025.100133. PMID: 41623364. PMC12859186.
116. Phan J, Tran C, Srinivasa S, Sebaratnam DF. Alpelisib for TEK- and PIK3CA-Related Venous Malformations: A Systematic Review. Australas J Dermatol. 2026. doi:10.1111/ajd.70178. PMID: 42402003.
117. Bollu V, LaGasse K, Saucier CD, Raymond K, Lauher-Charest M, Crowder L, et al. Health-Related Quality of Life and Symptom Severity Among Patients With PIK3CA-Related Overgrowth Spectrum: A Mixed-Methods Study to Understand Real-World Experience With Alpelisib Treatment. Pediatr Blood Cancer. 2026;73:e70368. doi:10.1002/1545-5017.70368. PMID: 42112579.
118. ClinicalTrials.gov. NCT05948943 — EPIK-L1, alpelisib in lymphatic malformations associated with a PIK3CA mutation. https://clinicaltrials.gov/study/NCT05948943
119. ClinicalTrials.gov. NCT05577754 — SESAM, alpelisib in MCAP (CHU Dijon). https://clinicaltrials.gov/study/NCT05577754
120. ClinicalTrials.gov. NCT05983159 — TARGET-VM (Murdoch Children's Research Institute). https://clinicaltrials.gov/study/NCT05983159
121. ClinicalTrials.gov. NCT07543822 — VATCH, alpelisib in TIE2/PIK3CA pathway vascular anomalies (CHOP). https://clinicaltrials.gov/study/NCT07543822
122. ClinicalTrials.gov. NCT06975618 — CYH33 in PROS and PIK3CA-related vascular malformations (Haihe Biopharma). https://clinicaltrials.gov/study/NCT06975618
123. ClinicalTrials.gov. NCT04409145 — topical VT30 in venous/lymphatic malformations with PIK3CA or TEK mutations (Venthera). https://clinicaltrials.gov/study/NCT04409145
124. Kalish JM, Doros L, Helman LJ, Hennekam RC, Kuiper RP, Maas SM, et al. Surveillance Recommendations for Children with Overgrowth Syndromes and Predisposition to Wilms Tumors and Hepatoblastoma. Clin Cancer Res. 2017;23:e115-e122. doi:10.1158/1078-0432.CCR-17-0710. PMID: 28674120. PMC5538793.
125. Stein SR, Perlow JH, Sawai SK. Klippel-Trenaunay-type syndrome in pregnancy. Obstet Gynecol Surv. 2006;61:194-206. doi:10.1097/01.ogx.0000201924.87671.90. PMID: 16490119.
126. Koch A, Aïssi G, Gaudineau A, Sananes N, Murtada R, Favre R, et al. [Klippel-Trenaunay syndrome and pregnancy: difficult choice of delivery from a case and a review of the literature]. J Gynecol Obstet Biol Reprod (Paris). 2014;43(7):483-7. doi:10.1016/j.jgyn.2013.11.016. PMID: 24461340.
127. Morin G, Fraissenon A, Chopinet C, Balducci E, Kaltenbach S, Villarese P, et al. First report of successful pregnancies after treatment with alpelisib for PIK3CA-related overgrowth spectrum. Eur J Hum Genet. 2025;33:1066-1071. doi:10.1038/s41431-025-01885-y. PMID: 40481231. PMC12322174.
128. Panteliades M, Resende Silva CM, Gontijo B. RETRACTION to "What is your diagnosis? CLOVES syndrome" An Bras Dermatol. 2016;91(3):378-80. An Bras Dermatol. 2026;101:501462. doi:10.1016/j.abd.2026.501462. PMID: 42805691.
129. Scott RH, Walker L, Olsen ØE, et al. Surveillance for Wilms tumour in at-risk children: pragmatic recommendations for best practice. Arch Dis Child. 2006;91:995-9. PMID: 16857697. https://pubmed.ncbi.nlm.nih.gov/16857697/