Follicular cheilitis. A distinctive histopathologic finding in actinic prurigo.

Actinic prurigo (AP), a chronic skin disease caused by an abnormal reaction to sunlight, is commonly associated with cheilitis and conjunctivitis. Characteristic ethnic, genetic, environmental (occurs at high altitudes, above 1,500 m), clinical, and histopathologic features have been reported. AP occurs in American Indians of Canada and the United States and most commonly in Latin American countries, where Mestizos (mixed ancestry) are predominantly affected. The present study investigates AP involving the lips, where it is characterized by a dense lymphocytic infiltrate, often with well-formed lymphoid follicles; the latter feature we refer to as "follicular cheilitis" (FC). The histopathologic findings of FC are characteristic of and helpful in diagnosing actinic prurigo involving the lips.