Unusual halo nevi - Darkening rather than lightening of the central nevus

Although the classic halo nevus is a brown nevus with a surrounding rim of depigmentation, i.e. a stage I halo nevus, these nevi can have several clin ical stages. The central nevus may lose its pigmentation and appear pink wi th a surrounding halo (stage II), the central papule may disappear leading to a circular area of depigmentation (stage III) or the depigmented area ma y repigment (stage IV), leaving no trace of its prior existence. Herein we describe an unusual phenomenon - darkening of the central nevus rather than lightening - following the appearance of the halo phenomenon. An 18-year-o ld boy who had multiple atypical nevi developed multiple halo nevi beginnin g at the age of 12 years. Following the appearance of the peripheral halos, 2 of his nevi that were originally solid medium brown in color darkened an d the hyperpigmentation had a reticulated pattern with perifollicular spari ng. One possible explanation is a postinflammatory hyperpigmentation induce d by the infiltrating lymphocytes. Copyright (C) 2001 S. Karger AG, Basel.