Multicentric reticulohistiocytosis.

Multicentric reticulohistiocytosis is a rare granulomatous disease of unknown etiology, characterized by cutaneous nodules and destructive arthritis. Skin lesions can cause significant deformity, and approximately half of affected patients develop a severe disabling arthritis. The disease is often associated with malignancy; however, the paraneoplastic nature of multicentric reticulohistiocytosis is not established. The diagnosis is confirmed by the presence of oncocytic ("ground-glass") histiocytes and multinucleated giant cells on histopathology of the cutaneous nodules and the synovial membrane.