Erdheim-Chester disease: hairy kidney and coated aorta

A 71-year-old man presented with unintentional weight loss and abdominal and back pain. Blood work revealed elevated serum creatinine (194 μmol/l; estimated glomerular filtration rate, 29 ml/min per 1.73 m2; Chronic Kidney Disease Epidemiology Collaboration formula), increased C-reactive protein, and anemia. Computed tomography demonstrated bilateral hydronephrosis grade III to IV and soft tissue surrounding both kidneys, including pelvis and the pyeloureteral junction (Figure 1a ). A circular thickening of the aortic wall with narrowing of the outlets of main abdominal and pelvic arteries was detected (Figure 1b). Positron emission tomography–computed tomography showed metabolic activity in the perirenal and periaortic tissue, bones, and testes (Supplementary Figure S1). Diagnosis of Erdheim-Chester disease was confirmed by histology of the tibial bone, showing histiocytic infiltration and fibrotic bone marrow cavities. Molecular analysis revealed a BRAFV600E mutation.