Kidney Involvement in Erdheim-Chester Disease

ECD is characterized by multisystem infiltration by foamy CD68+ CD1a− histiocytes and is driven by activating somatic mutations, most commonly BRAF V600E, together with significant immune dysregulation. Consequently, ECD is considered an inflammatory myeloid neoplasm, combining clonal hematopoietic proliferation with systemic inflammation. Clinical manifestations are highly heterogeneous and may involve long bones, the retroperitoneum, central nervous system, heart, large vessels, orbits, and endocrine organs. Renal involvement is common, occurring in up to 75% of patients, particularly in those harboring the BRAFV600E mutation. It typically affects the perirenal fat, producing the characteristic “hairy kidney” appearance on imaging. Infiltration of the renal pelvis and ureters may cause urinary obstruction, chronic kidney disease, and, less frequently, renovascular hypertension. Urinary tract infections are common and associated with substantial morbidity. Because renal involvement is often asymptomatic, diagnosis may be delayed, sometimes resulting in renal atrophy. At 5-year follow-up, a significant proportion of patients with perirenal involvement develop moderate to severe chronic kidney disease. This report presents a case of ECD with renal involvement and discusses its diagnostic work-up and management.