title: Unusual halo nevi--darkening rather than lightening of the central nevus.
abstract: 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 clinical stages. The central nevus may lose its pigmentation and appear pink with a surrounding halo (stage II), the central papule may disappear leading to a circular area of depigmentation (stage III) or the depigmented area may 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-old boy who had multiple atypical nevi developed multiple halo nevi beginning 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 and the hyperpigmentation had a reticulated pattern with perifollicular sparing. One possible explanation is a postinflammatory hyperpigmentation induced by the infiltrating lymphocytes.
authors.affiliation: Department of Dermatology, Yale University School of Medicine, New Haven, Conn 06520, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Huynh
authors.forename: R
authors.initials: R
authors.lastname: Lazova
authors.forename: J L
authors.initials: JL
authors.lastname: Bolognia
mesh_terms: D000293:Adolescent; D001415:Back; D006801:Humans; D017495:Hyperpigmentation / Q000473:pathology*; D008297:Male; D009508:Nevus, Pigmented / Q000473:pathology*; D012878:Skin Neoplasms / Q000473:pathology*