[Uncommon retroperitoneal and bone lesions: Erdheim-Chester disease].

We report a case of Erdheim-Chester disease, revealed by a polyuropolydipsic syndrome. During the patient's work-up, osteocondensing lesions were found; the biopsy of these lesions showed an infiltration by spumous cells of histiocytic lineage, CD68+, CD1a-, associated with a lymphoid infiltrate within an extensive fibrosis. Lung and retroperitoneal lesions were discovered. The surgical resection of the involved ureter was required. Histological examination of the resected specimen showed the same pattern of histiocytic infiltration. Our case report underlines the variety of lesions associated with Erdheim-Chester disease and the importance of a complete exploration.