Histopathology of Gottron's papules--utility in diagnosing dermatomyositis.

Dermatomyositis (DM) is an uncommon connective tissue disease that presents with a characteristic violaceous skin eruption as well as proximal muscle weakness, primarily of the upper extremities. Cutaneous stigmata of DM include Gottron's papules, similarly colored papules and plaques overlying the extensor surfaces of finger joints. While biopsy of the typical poikilodermatous skin eruption found in patients with suspected DM is a standard algorithmic component in the workup and diagnosis of the disease, Gottron's papules are rarely sampled for histopathologic assessment. The precise reason for this is not known but may be related to problems associated with healing because of constant motion forces in the vicinity of the joint. Given this, sparse literature is available on the histopathologic features of Gottron's papules. In this study, we present two cases in which the presence of papular (Gottron's papules) lesions on the fingers led to a presumptive diagnosis of DM and prompted biopsies of the same. The study illustrates the diagnostic utility of biopsies from Gottron's papules.