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Hamartoma · Blaschko-linearPaediatricICD-10 Q82.8

Epidermal naevus

Keratinocytic epidermal naevus · verrucous epidermal naevus · linear epidermal naevus · epidermal nevus

An epidermal naevus is a benign hamartomatous overgrowth of epidermis, usually present at birth or arising in early childhood. Linear lesions follow Blaschko lines and often start as flat tan-brown marks before becoming thickened, papillomatous or warty. Most are isolated and benign. The clinical task is to recognise persistent Blaschko-linear epidermal lesions, separate them from inflammatory mimics such as lichen striatus and linear psoriasis, and identify extensive/systematised lesions or extracutaneous features that suggest an epidermal naevus syndrome.

CurrentLast reviewed 5 June 2026
Clinical image of Epidermal naevus
Epidermal naevus. Image sourced from DermNet New Zealand. Used under CC BY-NC-ND 4.0. No endorsement implied.

Biology and classification

  • Most lesions are keratinocytic epidermal naevi: hamartomatous overgrowth of keratinocytes.
  • Post-zygotic mosaicism explains the Blaschko-linear distribution; reported genes include FGFR3, PIK3CA and HRAS, depending on phenotype.
  • Recognised patterns include linear epidermal naevus, systematised epidermal naevus, epidermolytic epidermal naevus, acantholytic epidermal naevus and linear porokeratosis-like lesions.
  • When appendageal structures predominate, the term organoid naevus is used, including sebaceous naevus and naevus comedonicus.
  • ILVEN is often considered separately: pruritic, erythematous and inflammatory, usually along Blaschko lines.

Clinical features

  • About half are present at birth; many others appear during infancy or early childhood.
  • Usually unilateral, linear or whorled along Blaschko lines on trunk or limbs; face/scalp involvement is less common for ordinary keratinocytic lesions.
  • Early lesions may be flat tan or brown macules/patches; with age they become thicker, papillomatous, verrucous or hyperkeratotic.
  • May enlarge proportionately with growth and can become more conspicuous around puberty.
  • Most are asymptomatic; itch, erythema and psoriasiform inflammation suggest ILVEN or an inflammatory mimic.

Syndrome red flags

  • Extensive, systematised, bilateral or very large lesions need a broader review for extracutaneous abnormalities.
  • Epidermal naevus syndromes can involve the central nervous system, eyes and skeleton; examples include Schimmelpenning syndrome, naevus comedonicus syndrome, CHILD syndrome and Proteus/CLOVES-spectrum disorders.
  • Ask about seizures, developmental delay, headaches, visual symptoms, limb asymmetry, scoliosis, bony overgrowth and recurrent infections.
  • Consider paediatric dermatology/genetics referral when lesions are extensive, syndromic features are present, or the diagnosis overlaps with vascular/overgrowth syndromes.

Differential diagnosis

  • Lichen striatus: usually acquired, inflammatory, self-limiting and more common in children.
  • Linear lichen planus, linear psoriasis or linear porokeratosis.
  • ILVEN: intensely pruritic, persistent, inflammatory and often treatment-resistant.
  • Incontinentia pigmenti: staged vesicular, verrucous and pigmentary evolution, typically in female infants.
  • Naevus sebaceus, naevus comedonicus, Becker naevus and connective-tissue naevi.
  • Verruca vulgaris, especially if a localised verrucous lesion appears later in life.

Management

  • Reassure for small, stable, asymptomatic lesions.
  • Emollients and keratolytics can help scale/roughness; topical calcipotriol or topical retinoids may reduce thickness in selected cases but responses are variable.
  • Topical corticosteroids/calcineurin inhibitors are useful only for inflammatory components, not for the naevus itself.
  • Laser ablation, shave/dermabrasion or excision can be considered for symptoms, repeated trauma, diagnostic uncertainty or appearance, but counsel about scarring and recurrence.
  • Biopsy any new nodular, ulcerated, bleeding, rapidly changing or atypical focus within a longstanding lesion.

References

  1. DermNet. Epidermal naevi.
  2. MedlinePlus Genetics. Epidermal nevus.
  3. NCBI Bookshelf. Epidermal Nevus Syndromes.
  4. Groesser L et al. Postzygotic HRAS and KRAS mutations cause naevus sebaceous and Schimmelpenning syndrome. Nat Genet. 2012;44:783-787.

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