Renal calculi in a patient with Erdheim-Chester disease.

Erdheim-Chester Disease (ECD) is a non-inherited multifocal lipid storing histiocytosis. It is a rare disease characterised by lipid-laden monocyte infiltration of long bones causing cortical sclerosis and characteristic X-ray appearances. It also involves extraskeletal tissue in up to 50% of cases including retroperitoneal and renal infiltration. We report a patient with long standing ECD with widespread extraskeletal involvement, including significant renal infiltration, presenting with left hydronephrosis secondery obstruction from a proximal ureteric calculas.