Histopathology of Gottron's papules

We studied Gottron's papules in 11 cases of known dermatomyositis to determine whether the findings were similar to those in the poikilodermatous eruption usually biopsied in this disease. As in typical poikilodermatous dermatomyositis, basal layer vaculopathy, PAS-positive basement membrane thickening, upper dermal mucin deposition and a mild diffuse upper dermal mononuclear infiltrate were frequent findings. In contrast to poikilodermatous dermatomyositis, however, epidermal hyperplasia consisting of acanthosis or papillomatosis was often present and epidermal atrophy was rare. We conclude that a specific diagnosis of dermatomyositis can often be made on biopsy of a Gottron's papule.