[IgG4-related kidney disease: a long-term follow up case of pseudotumor of the renal pelvis].

A 69-year-old man had undergone left ureteronephrectomy because of a left renal pelvic tumor, however the pathological diagnosis was inflammatory pseudotumor. About 1 year later, computed tomography showed a mass at the right kidney near the hilar. Ureterorenoscopy and urine cytology were performed, and their results showed no evidence of malignancy. He had been followed closely without therapy. The mass increased in size during follow-up, and we reviewed the surgical specimen of the left ureteronephrectomy. Immunohistochemical studies revealed diffuse infiltration by IgG4 positive plasma cell. His serum IgG4 was high. We diagnosed him as IgG4-related kidney disease. In response to treatment with corticosteroid, the size of the tumor and serum IgG4 levels decreased. Most reported cases of IgG4-related disease involving kidney have a history of prior pancreatic involvement. We report a rare long term follow-up case of IgG4-related kidney disease without pancreatic involvement.