Linear epidermal nevus - Hair and Scalp
One specific subtype, the linear epidermal nevus, is not uncommon. Linear epidermal nevi tend to fall along relaxed skin tension lines, or in Blaschko's lines.
Histologically, linear epidermal nevi are benign growths comprised of keratinocytes, apocrine glands, eccrine glands, sebaceous glands, or components of pilosebaceous units.
Lesions occur sporadically, although they may also occur as a component of several syndromes. There is an equal prevalence between both sexes. Epidermal nevi tend to appear between birth and adolescence.
Linear epidermal nevi are traditionally asymptomatic, but a specific subtype called inflammatory linear verrucous epidermal nevus (ILVEN) can be associated with pruritus, erythema, and scaling.
Epidermal nevi comprise a heterogeneous group of diseases. Nomenclature and classification is confusing and controversial. Six different epidermal nevus syndromes have been described:
- Nevus sebaceous – Relatively common, these represent roughly 50% of epidermal nevi. Typically present at birth, they undergo thickening and papillomatous changes at puberty. After puberty, these can be associated with basal cell carcinoma. The syndrome implies CNS involvement, which seems to be related to extent of nevus and location.
- CHILD syndrome – Congenital hemidysplasia with ichthyosiform nevus and limb defect. Thought to be X-linked dominant. Unilateral inflammatory erythematous plaques with overlying yellow scale. Often occurs in body folds and is associated with ipsilateral limb hypoplasia.
- Nevus comedonicus – Localized collection of dilated follicles containing keratin. Can be found on the face, trunk, and upper extremities. Follicular tumors have been reported within these and are rarely associated with EEG abnormalities, skeletal abnormalities, and cataracts.
- Becker's nevus – Focal area of hyperpigmentation with hypertrichosis. Can have a pseudo-Darier's sign when stroked. Typically seen in late childhood or adolescence. Syndrome can be associated with skeletal abnormalities, hypoplasia of breast/musculature, and others.
- Proteus syndrome – Complex syndrome including overgrowth of multiple tissues with one diagnostic criterion including epidermal nevi.
- Phacomatosis pigmentokeratotica – Syndrome including speckled lentiginous nevi, hemiatrophy with muscle weakness, as well as epidermal nevi, among other criteria.
D23.9 – Other benign neoplasm of skin, unspecified
399995006 – Inflammatory linear verrucous epidermal nevus