[Case of IgG4-related tubulointerstitial nephritis showing the progression of renal dysfunction after a cure for autoimmune pancreatitis].

A 78-year-old-man was admitted to our hospital because of renal insufficiency 20 months after the onset of autoimmune pancreatitis. He had cerebral infarction and prostatic hypertrophy as complications. He had been previously diagnosed with autoimmune pancreatitis (AIP). The initial therapy was started with oral prednisolone at the dose of 0.8 mg/kg (40 mg/day). Prednisolone had been tapered off gradually through a one-year period. Four months later from terminating prednisolone, a follow-up CT showed multiple low-density areas in both kidneys without swelling of the pancreas. Furthermore, 4 months later, laboratory findings showed progressive renal insufficiency. On admission, BP was 167/77 mmHg, and the bilateral submaxillary glands were swollen. He did not have pretibial edema. Laboratory findings were as follows. BUN 55.9 mg/dL, Cre 6.17 mg/dL, Amy 65 mg/dL, TP/Alb 9.5/4 g/dL, gamma-gl 43.7%, IgG/IgA/IgM 3,395/112/74 mg/dL, IgG4 1,460 mg/dL, urinary protein 1.38 g/day, and 24 hr-Ccr 11.8 mL/min/1.73 m2. Percutaneous renal needle biopsy was conducted. Light microscopic findings demonstrated tubulointerstitial nephritis (TIN) and membranous change. Immunofluorescent microscopic findings indicated diffuse deposition of IgG2 and IgG4 in the renal interstitium. On the basis of these findings, the condition was diagnosed as IgG4-related tubulointerstitial nephritis. As renal insufficiency was progressing, hemodialysis was started soon after admission and oral prednisolone was also started at the dose of 0.4 mg/kg (20 mg/day). However, improvement of renal function has not been obtained and hemodialysis and prednisolone tapering are still being conducted. This case showed severe tubulointerstitial nephritis requiring hemodialysis after a cure for autoimmune pancreatitis. IgG4-related renal disease rarely needs hemodialysis. This case indicates that the prognosis of IgG4-related systemic disease is not necessarily good and further accumulation of cases is required.