Erdheim-Chester disease: pulmonary infiltration responding to cyclophosphamide and prednisolone.

Erdheim-Chester disease is a rare multisystem histiocytic disorder in which death most commonly results from pulmonary or cardiac involvement. We report the case history of a 55 year old man with this condition with extensive and progressive pulmonary disease. He had no response to prednisolone alone, but treatment with prednisolone plus cyclophosphamide was associated with a rapid improvement in symptoms, lung function, and the chest radiographic appearance. He subsequently showed a symptomatic, functional, and radiological deterioration, followed by a marked slowing in the rate of decline. He currently remains stable 41 months after treatment was initiated. This is the first report of pulmonary Erdheim-Chester disease showing improvement in both lung function and symptoms with any form of treatment.