Epidermal Nevus

The term epidermal nevus is commonly used to describe a group of cutaneous hamartomas linked by common clinical and histologic features. Linear epidermal nevus or nevus unius lateris (a linear, unilateral, wartlike nevus), nevus verrucosus (a localized, wartlike nevus), and ichthyosis hystrix (an irregular, bilateral, truncal nevus) are some of the names given to variants of epidermal nevus. Inflammatory linear verrucous epidermal nevus (ILVEN) is characterized by intensely erythematous, pruritic, inflammatory papules that occur as linear bands along the lines of Blaschko. The term nevus means a congenital defect of the skin characterized by the localized excess of one or more types of cells. Histologically the cells are identical to or closely resemble normal cells. Epidermal nevus should be used as a general term to designate an excess of one type of epidermally derived cells (e.g., squamous cell or sebocyte). However, the term is commonly reserved for congenital growths in which the predominant cell is the keratinocyte. These nevi arise from the pluripotential germinative cells in the basal layer of the embryonic epidermis. These cells give rise to keratinocytes and skin appendages (hair follicles, sweat glands).