Immunoglobulin G4 (IgG4)-related kidney disease is a chronic immune-mediated fibro-inflammatory disorder characterized by multiple organ infiltration with IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis or tumefactive lesions.
Previous studies have explored IgG4-related kidney disease, increasing our understanding of its clinical manifestations, and pathological and radiologic findings. However, IgG4-related kidney disease can be misdiagnosed since it mimics malignancies. We report a case of a 77-year-old Korean man diagnosed with IgG4-related kidney disease with membranous proliferative glomerulonephritis, presenting with a renal pelvic mass suspected of being malignant.