Diffuse cutaneous reticulohistiocytosis.

A 65-year-old man had a diffuse, asymptomatic, cutaneous eruption of 5- to 15-mm reddish-brown, nonscaling papules in arcuate, annular, and serpiginous patterns for one year. The morphologic, light microscopic, and ultrastructural features of the skin lesions were typical of multicentric reticulohistiocytosis; however, the patient had no historic, clinical, laboratory, or roentgenographic evidence of arthritis. Spontaneous involution of the eruption occurred 17 months after onset. Several weeks later subacute myelogenous leukemia developed. The reported occurrence of isolated and multiple reticulohistiocytomas, diffuse cutaneous reticulohistiocytosis without systemic involvement, and multicentric reticulohistiocytosis with identical light microscopic and ultrastructural findings suggests that these conditions probably represent a spectrum of clinical expressions of similar etiologic and pathogenetic mechanisms.