Late onset hairy nevus with perifollicular hypermelanosis.

Abstract

The nevus described here can be easily differentiated from other nevi with hypertrichosis as congenital melanocytic nevus, nevus leiomyoma, plexiform neurofibroma, due to its late onset, dotted hyperpigmentation and especially for the absence of melanocytes, muscle cells and nerve cells in the dermis. The hairy nevus itself is characterized by early onset and lack of hyperpigmentation. The localized congenital hypertrichosis, in addition to being present at birth and not pigmented affects other locations. Becker's nevus differs for uniform hyperpigmentation, for the presence of hypertrophic hairs only on a part of the nevus and the lack of multiple hair follicles in the pilaris unit. However, Becker's nevus shares the late onset with the hairy nevus with perifollicular hypermelanosis here described.