Pruritic brownish confluent reticulated papules over the trunk of a 30-year-old woman

Abstract

Conflict of interest: none declared. A 30‐year‐old woman presented with a 13‐year history of a pruritic erythematous maculopapular eruption distributed symmetrically over the chest, back and posterior neck. Recurring bouts of pruritic papules had left striking reticular hyperpigmented patches on the affected areas (Fig. 1). ... A skin biopsy was taken from an erythematous papule surrounded by hyperpigmented macules on the upper back. Histological examination under low magnification showed acanthosis and a superficial perivascular infiltration of inflammatory cells, and under higher magnification, spongiosis, lymphocytic exocytosis and vacuolar degeneration of the basal cell layer was seen (Fig. 2). ... What is your diagnosis? Prurigo pigmentosa (PP), late stage. PP is a rare inflammatory dermatosis of unknown aetiology. It was first reported in Japan, where it is found most commonly; it is rare in western countries. The clinical features are symmetrical and intensely pruritic erythematous papules, papulovesicles and vesicles appearing in a reticular pattern with a predilection for the upper part of the back, neck, shoulders, lumbosacral region and abdomen. The lesions involute in a matter of days, leaving reticulate pigmentation.1