Immunoglobulin G4-related sclerosing disease presenting as a rare cause of renal pelvic mass mimicking malignancy

Immunoglobulin G4-related sclerosing disease is a recently recognized disease entity most commonly associated with autoimmune pancreatitis. This condition can also manifest as extra-pancreatic disease involving the bile ducts, kidney, lung, and retroperitoneum. The disease entity consists of elevated serum IgG4 levels, extensive IgG4-positive plasma cells, and lymphocyte infiltration of the affected organs. We describe the clinical and radiographic presentation and pathologic findings in a patient with isolated renal involvement in IgG4-related sclerosing disease.