Membranoproliferative glomerulonephritis-like glomerular disease and concurrent tubulointerstitial nephritis complicating IgG4-related autoimmune pancreatitis.

Autoimmune pancreatitis is characterized by diffuse enlargement of the pancreas, irregular narrowing of the pancreatic duct, high serum levels of IgG4, and lymphoplasmacytic infiltration in the pancreatic parenchyma. Accumulating evidence suggests that this autoimmune disease could present with diffuse infiltration of IgG4-positive plasmacytes in multiple organs. Recently, a new concept of IgG4-related systemic disease including autoimmune pancreatitis, characterized by high serum IgG4 level and tissue infiltration by IgG4-positive plasma cells, has been proposed. Renal lesions in IgG4-related diseases have been reported recently. Most of them are tubulointerstitial nephritis; however, glomerulonephritis associated with IgG4-related diseases is very rare. We describe here a patient with membranoproliferative glomerulonephritis-like glomerular disease, together with tubulointerstitial nephritis, idiopathic thrombocytopenic purpura, and autoimmune pancreatitis. An 80-year-old Japanese man was referred to our hospital with a 14-month history of proteinuria, and a progressively rising serum creatinine level. Renal biopsy revealed membranoproliferative glomerulonephritis-like glomerular disease and concurrent tubulointerstitial nephritis. Immunolabeling of renal tissue showed numerous IgG4-positive plasma cells in the interstitium. The rare association between glomerulonephritis and IgG4-related systemic disease is discussed.