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A benign, pigmented skin growth caused by an overgrowth of the epidermis. It is typically seen at birth, but can develop in early childhood or later in life. Most cases are sporadic, but familial patterns of inheritance have been observed.
Features include: Numerous nevi and Melanocytic nevus.
PIK3CA-related overgrowth spectrum (PROS) includes overgrowth of a broad range of tissues that may or may not be accompanied by cellular dysplasia. Prior to the understanding of the molecular nature of PROS, a number of distinct but overlapping phenotypes were clinically described and given names . In general, PROS can be divided into an isolated form (when a person has a focal lesion that affects only one tissue or body part; see ) and a syndromic form (i.e., overgrowth plus at least two other features in two systems; see ). A targeted therapy aimed at inhibiting PI3K-related pathway overgrowth has been approved by the FDA . Table 2. Selected Isolated PIK3CA-Related Overgrowth Phenotypes by Affected Organ or Tissue
Organ or Tissue | Phenotype | Comment |
|---|---|---|
Brain/Head | HMEG: brain overgrowth affecting 1 hemisphere w/or w/o cortical dysplasia | Cognitive developmental disabilities; Seizures are common.; Focal neurologic deficits may be present.; May result in facial asymmetry Focal cortical dysplasia1 |
Limb | Hemihyperplasia | May incl whole limb, part of limb, or only hand or foot (acral overgrowth); May involve soft tissue, muscle, /or bone Macrodactyly |
Lymphatics7 | Isolated lymphatic malformations: dilated vascular channels lined by lymphatic endothelial cells | Fluid-filled cysts usually grow proportionally w/growth of affected person; may pain /or morbidity if they are infiltrative. |
Vascular7 | Vascular malformations | Incl capillary, venous, or mixed malformations Skin |
Source: GeneReviews — "PIK3CA-Related Overgrowth Spectrum"
FGFR3 encodes fibroblast growth factor receptor 3 (806 aa). Tyrosine-protein kinase that acts as a cell-surface receptor for fibroblast growth factors and plays an essential role in the regulation of cell proliferation, differentiation and apoptosis. Highest expression in Skin Not Sun Exposed Suprapubic (364.5 TPM) and Skin Sun Exposed Lower leg (356.5 TPM).
Nevus, epidermal is associated with mutations in the FGFR3 gene on chromosome 4.
FGFR3 is classified as a druggable target (Cell Surface, Clinically Actionable, Drug Resistance, Druggable Genome, Kinase, and Tyrosine Kinase categories) with score 1.6.
HRAS encodes HRas proto-oncogene, GTPase (189 aa). Involved in the activation of Ras protein signal transduction. Ras proteins bind GDP/GTP and possess intrinsic GTPase activity
Nevus, epidermal is associated with mutations in the HRAS gene on chromosome 11.
The HRAS protein participates in S-farn Me-HRAS, -NRAS and -KRAS4A are palmitoylated pathway.
HRAS is classified as a druggable target (Clinically Actionable, Drug Resistance, Druggable Genome, Enzyme, and Tumor Suppressor categories) with score 0.8.
NRAS encodes NRAS proto-oncogene, GTPase (189 aa). Ras proteins bind GDP/GTP and possess intrinsic GTPase activity Highest expression in Cells EBV-transformed lymphocytes (77.3 TPM) and Cells Cultured fibroblasts (52.5 TPM).
Nevus, epidermal is associated with mutations in the NRAS gene on chromosome 1.
The NRAS protein participates in S-Farn-Me KRAS4A, HRAS, NRAS and S-Farn-Me PalmS KRAS4A,HRAS, NRAS pathways.
NRAS is classified as a druggable target (Clinically Actionable, Drug Resistance, and Enzyme categories) with score 0.8.
PIK3CA function has not been fully characterized.
Nevus, epidermal is associated with mutations in the PIK3CA gene on chromosome 3.
PIK3CA-related overgrowth spectrum (PROS) encompasses a range of clinical findings in which the core features are congenital or early-childhood onset of segmental/focal overgrowth with or without cellular dysplasia in the absence of a family history of similarly affected individuals (i.e., single occurrence in a family). Prior to the identification of PIK3CA as the causative gene, PROS was separated into distinct clinical syndromes based on the tissues and/or organs involved .
PROS should be considered in individuals with the following clinical, brain MRI, and family history findings .
Clinical features
Source: GeneReviews — "PIK3CA-Related Overgrowth Spectrum"
A number of overgrowth and megalencephaly disorders overlap with the PIK3CA-related overgrowth spectrum (PROS), including those summarized in . Table 4. Genes of Interest in the Differential Diagnosis of PIK3CA-Related Overgrowth Spectrum (PROS)
Gene(s) | Disorder | MOI | Clinical Features of Disorder |
|---|---|---|---|
Proteus syndrome | NA (somatic) | Focal somatic overgrowth, epidermal nevi, vascular malformations, dysplastic adipose tissue | Cerebriform connective tissue nevi postnatal onset of overgrowth (vs congenital onset in PROS). Absence of characteristic truncal fatty-vascular mass, spinal paraspinal fast-flow lesions, acral abnormalities of CLOVES syndrome AKT3 CCND2 PIK3R2 |
Genetic testing for FGFR3, HRAS, NRAS, PIK3CA is available. Testing is considered confirmatory for diagnosis.
Biomarker and diagnostic research for nevus, epidermal has been reported in the published literature.
No approved treatments are currently available for nevus, epidermal. The disease remains an area of unmet medical need.
Gene therapy approaches for nevus, epidermal have been reported in the published literature.
Clinical practice guidelines for PIK3CA-related overgrowth spectrum have been published (full text). Additionally, a targeted pharmacologic therapy has been FDA approved .
To establish the extent of disease and needs in an individual with PIK3CA-related overgrowth spectrum (PROS), the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended. Note: Assessment is complicated by variable findings in individuals with this condition. Accurate and thorough assessment of medical history is necessary to evaluate for vascular malformations as well as other clinical features.
Table 5.
Recommended Evaluations Following Initial Diagnosis in Individuals with PIK3CA-Related Overgrowth Spectrum
System/Concern | Evaluation | Comment
Constitutional
(overgrowth) | Measure growth parameters incl head circumference, total body length, length of arms, hands, legs feet. | To assess for generalized segmental overgrowth (incl leg length discrepancy) macrocephaly
Consider whole-body MRI. | In those w/truncal overgrowth
Consider limb radiographs subsequent limb MRI. | In those w/segmental or generalized overgrowth of a limb
Consider spinal ultrasound in infants spinal MRI (w/MR angiography) in older persons. | In those w/evidence of spinal involvement (See also Cardiovascular/Vascular in this table.)
Clinical assessment for pain functional impairment |
Constitutional
(undergrowth
or generalized
growth
Source: GeneReviews — "PIK3CA-Related Overgrowth Spectrum"
View trials for nevus, epidermal
Table 8. Recommended Surveillance for Individuals with PIK3CA-Related Overgrowth Spectrum
System/Concern | Evaluation | Frequency |
|---|---|---|
restriction) | Measurement of growth parameters, incl head circumference, length of arms, hands, legs,1 feet2 | At each visit; Ultrasound or MRI follow up in those w/truncal overgrowth2; Radiographs of limbs in those w/overgrowth of a limb or portion of a limb; Spinal MRI in those w/scoliosis or deformities that affect the spine |
Neurologic | Serial head MRI imaging | Depending on severity of findings on initial assessment degree of brain maturation3; Monitor those w/seizures as clinically indicated.; Assess for new manifestations incl seizures, changes in tone, other signs/symptoms of Chiari malformation.4,5 |
Behavioral | Behavioral assessment for anxiety, attention, aggressive or self-injurious behavior | At each visit in children, adolescents, adults Musculoskeletal |
malformations | Clinical assessment monitoring, ideally by a vascular anomalies team6 | As clinically indicated |
Genitourinary | Consideration of renal ultrasound | Every 3 mos until age 8 yrs7 |
Hematologic | Hematology consultation w/recommendations for assessment for thrombosis coagulopathy risk | After any surgical intervention, esp in those w/CLOVES phenotype /or vascular malformations Endocrinologic |
Source: GeneReviews — "PIK3CA-Related Overgrowth Spectrum"
No clinical trials have been registered for nevus, epidermal.
140 publications have been identified in PubMed for nevus, epidermal. Research spans Case Report / Case Series (60%), Review / Meta-Analysis (15%), and Other (6%).
Research Type | Count | % of Total |
|---|---|---|
Patient case studies | 84 | 60% |
Research summaries | 21 | 15% |
Other research | 8 | 6% |
Disease patterns and progression | 8 | 6% |
Laboratory research | 7 | 5% |
Clinical study results | 6 | 4% |
New treatment approaches | 4 | 3% |
Testing and diagnosis research | 2 | 1% |
Pei X (2026). [PMID: 41335415](https://pubmed.ncbi.nlm.nih.gov/41335415/). *JAMA dermatology*. [Case Report / Case Series]
Luo AJ (2026). [PMID: 42028865](https://pubmed.ncbi.nlm.nih.gov/42028865/). *Br J Dermatol*. [Basic Science / Preclinical]
Gao W (2026). [PMID: 40974197](https://pubmed.ncbi.nlm.nih.gov/40974197/). *J Eur Acad Dermatol Venereol*. [Case Report / Case Series]
Ashraf F (2026). [PMID: 42043770](https://pubmed.ncbi.nlm.nih.gov/42043770/). *Indian Pediatr*. [Other]
Inamadar A (2026). [PMID: 41318891](https://pubmed.ncbi.nlm.nih.gov/41318891/). *Journal of cutaneous medicine and surgery*. [Case Report / Case Series]
Pszczółkowska A (2026). [PMID: 41511744](https://pubmed.ncbi.nlm.nih.gov/41511744/). *Dermatol Ther (Heidelb)*. [Basic Science / Preclinical]
Chen L (2026). [PMID: 42110453](https://pubmed.ncbi.nlm.nih.gov/42110453/). *Front Med (Lausanne)*. [Case Report / Case Series]
Singh S (2026). [PMID: 41494726](https://pubmed.ncbi.nlm.nih.gov/41494726/). *BMJ case reports*. [Case Report / Case Series]
Ramphul K (2026). [PMID: 29939590](https://pubmed.ncbi.nlm.nih.gov/29939590/). *Unknown Journal*. [Other]
Dua Y (2026). [PMID: 41923345](https://pubmed.ncbi.nlm.nih.gov/41923345/). *ANZ J Surg*. [Review / Meta-Analysis]
Data assembled from 6 of 12 sources · Last updated Sep 19, 2026, 12:59 PM UTC
Online Mendelian Inheritance in Man
Megalencephaly-polydactyly-polymicrogyria-hydrocephalus (MPPH) syndrome |
AD (de novo) or somatic |
Brain overgrowth (MEG), polymicrogyria, hydrocephalus, polydactyly, connective tissue or joint laxity |
Absence of consistent vascular/lymphatic malformations or severe focal somatic overgrowth HRAS KRAS |
NRAS | Linear nevus sebaceous syndrome (LNSS) (OMIM 163200) | NA (somatic) | Cutaneous findings (incl epidermal nevi vascular malformations) |
Smith-Kingsmore syndrome | AD (de novo) or somatic | Brain overgrowth (MEG), polymicrogyria, cutaneous findings (incl hyperpigmented nevi) | Absence of consistent vascular/lymphatic malformations PTCH1 SUFU |
Basal cell nevus syndrome | AD | Brain overgrowth (MEG), polydactyly, syndactyly | Calcine calcification, BCCs, jaw cysts, epidermal cysts, wide ribs, many other skeletal other multisystem features |
PTEN | PTEN hamartoma tumor syndrome (PHTS) | AD | Brain overgrowth (MEG), vascular malformations (incl capillary malformations), lipomas |
Source: GeneReviews — "PIK3CA-Related Overgrowth Spectrum"