Membranous nephropathy associated with IgG4-related systemic disease and without autoimmune pancreatitis.

We describe an elderly man with membranous nephropathy and lymphoplasmacytic infiltration into the renal interstitium who presented with a high serum IgG4 concentration and no organ involvement in the pancreatobiliary system. Although the patient had hypocomplementemia and was positive for antinuclear antibodies, he was negative for antibodies against Sm, SS-A, SS-B and RNP, and his anti-DNA antibody titer was not elevated. Immunohistochemistry demonstrated that the infiltrated plasma cells in the renal interstitium and glomerular capillary walls were strongly positive for IgG4. Electron microscopy showed electron-dense deposits on the glomerular basement membranes and tubular basement membranes. The present case suggests that membranous nephropathy, like tubulo-interstitial nephritis, is one of the renal features of IgG4-related systemic disease.