A 72-year-old woman was admitted to our hospital because of massive proteinuria of 2.2 g/day. She had seen a general practitioner for management of Basedow disease, diabetes mellitus and hypertension for 24 years. On admission, she complained of anorexia and nausea. Laboratory data showed serum creatinine of 3.62 mg/dL and MPO-ANCA of 68 EU. Renal biopsy revealed crescentic glomerulonephritis complicated with membranous nephropathy. Thiamazole (MMI), which was being given for Basedow disease for years, was withdrawn on the suspicion as a cause of MPO-ANCA. Three years after the withdrawal of MMI, renal failure slowly progressed to the end-stage, while MPO-ANCA was negative. She was introduced onto hemodialysis. At that time, MPO-ANCA became positive again, the titer being 12.9 EU. Therefore, we suspected a relapse of ANCA-related vasculitis and performed steroid pulse therapy on the patient with methylprednisolone at 0.5 g/day for 3 days. On hospital day 14, MPO-ANCA became negative. On day 25, however, severe acute pancreatitis developed and a pancreatic tumor lesion was found on CT. In spite of amelioration of the pancreatitis by medical treatment, the pancreatic tumor lesion did not show any significant change. On day 48, she died of multiple organ failure. Autopsy showed a mucinous cyst adenoma of pancreas and necrotizing pancreatitis. We suspected steroid therapy as the cause of the pancreatic lesions.