Appearance of Verruca Over Linear Verrucous Epidermal Nevus - An Example of Locus Minoris Resistentiae: A Report of Three Cases.

Locus minoris resistentiae (LMR) is a site of the body that offers lesser resistance than the rest of the body to the onset of disease. It can be congenital or acquired. Areas of cutaneous mosaicism such as epidermal nevi can act as congenital LMR, leading to the development of inflammatory skin conditions or skin tumors on these. The occurrence of an infectious condition such as warts over nevi is rare. We report three cases of verrucous epidermal nevi (VENs) with the development of verrruca overlying the nevus later in life. The three patients had VEN on forehead, preauricular, and presternal area, respectively, since birth, with development of a warty lesion overlying these a few months before presenting to us. Skin biopsy and histopathological examination of the linear verrucous lesion were suggestive of VEN with hyperkeratosis, thickened epidermis, and papillomatosis. There was no evidence of epidermolytic hyperkeratosis or increased sebaceous glands in the dermis. Biopsy of the new warty lesion showed findings of verruca in all the patients. With the above findings, a diagnosis of verruca superimposed on linear VEN was made in all the three cases. The warts were removed by electrofulguration. Several acquired skin disorders, including inflammatory dermatoses, adnexal disorders, and neoplasms, have been shown to occur superimposed on epidermal or sebaceous nevus. Ours is probably the first ever description of a wart occurring on VEN.