A case of tubulointerstitial nephritis in IgG4-related systemic disease with markedly enlarged kidneys.

IgG4-related systemic disease, including autoimmune pancreatitis, is a multi-organ disorder characterized by elevated serum immunoglobulin G4 (IgG4) concentration and IgG4-positive plasma cell infiltration. We report the case of a 67-year-old man with IgG4-related tubulointerstitial nephritis, presenting with markedly enlarged kidneys and renal dysfunction. The serum IgG4 level was elevated with 4200 mg/dl and pathological examination revealed patchy, clearly fringed areas of IgG4-positive plasma cell infiltration and advanced fibrosis in the renal parenchyma, perirenal tissue and lymph nodes. With oral prednisolone at a dose of 60 mg daily, a contraction of the kidneys and an improvement of renal function were observed. No recurrence of the disease was observed during the reduction of prednisolone to 2 mg daily over 4 years.