Lichen planus pigmentosus inversus.

Twenty-five year old male patient presenting with asymptomatic brown spots, on cervical, axillary, inguinal and popliteal regions, for the last nine months. Pathological examination showed hydropic degeneration of the basal layer, pigmentary incontinence and moderate inflammatory lymphocytic infiltrate in the dermis. Lichen planus pigmentosus inversus is a rare subtype of lichen planus characterized by hyperchromic, asymptomatic or mildly pruritic macules, measuring from millimeters to centimeters in diameter, with defined borders, affecting intertriginous areas, most commonly in the axillae and groin of Caucasian patients. It presents unique lichenoid histology. We report a case with typical clinical features, histology and evolution.