Epidermal nevus

Epidermal nevi are congenital lesions that affect about 1 in 1,000 people. They appear at or shortly after birth as localized epidermal thickening with hyperpigmentation that frequently follow the lines of Blaschko, suggesting that they result from postzygotic somatic mutation in the skin (Paller et al., 1994). A rare subgroup of epidermal nevi is clinically indistinguishable from other epidermal nevi, but displays histopathologic features typical of epidermolytic hyperkeratosis (see EHK, 113800), and patients with this type of epidermal nevi sometimes have offspring with generalized EHK (Paller et al., 1994). Woolly hair nevus is a rare condition characterized by the development of woolly hair in a restricted area on the scalp, either present at birth or becoming evident later in life when scalp hair begins to grow. Woolly hair nevus can be an isolated finding or can occur in association with additional ectodermal defects; epidermal nevi have been reported in association with woolly hair nevi (summary by Ramot and Zlotogorski, 2015). Nevus sebaceous, a benign congenital skin lesion that preferentially affects the scalp and face, is characterized by hairless, yellow-orange plaques of various size and shape. Histology shows that nevus sebaceous is a hamartoma consisting of epidermal, sebaceous, and apocrine elements. About 24% of nevi develop secondary tumors, some of which may be malignant (summary by Groesser et al., 2012). Also see giant pigmented hairy nevus (137550) and malignant melanoma (155600).

OMIM