IgG4-related Chronic Tubulointerstitial Nephritis without Autoimmune Pancreatitis and the Time Course of Renal Function

We report an elderly man with chronic tubulointerstitial nephritis (TIN) showing a high serum immunoglobulin G4 (IgG4) concentration. His serum creatinine (Scr) level had gradually increased from 0.9 mg/dL to 5.6 mg/dL over 18 months. Renal biopsy showed marked IgG4-positive plasma cell infiltration in the interstitium without glomerular abnormalities and IgG4-related TIN was diagnosed. Oral prednisolone reduced his Scr and IgG4 levels immediately. The present case indicates that IgG4-related TIN can not only progress rapidly but also chronically over a long period without significant urinary abnormalities, and we should consider hidden IgG4-related TIN in cases of chronic renal insufficiency.