title: IgG4-related tubulointerstitial nephritis accompanied with cystic formation.
abstract: BACKGROUND
  An immunoglobulin G4 (IgG4)-related disease is important disease in differential diagnosis of tumors in kidney, pancreas, lung and other organs. The imaging findings of IgG4-related kidney diseases are usually expressed as defect contrast region, while cystic formation in kidney is extremely rare. Here, we report a case of IgG4-related tubulointerstitial nephritis with renal cystic change caused by the narrowing or obstruction of collecting duct in renal medulla.
  
  
  METHODS
  Abdominal contrasted CT scan showed a 31 × 24 mm cystic tumor at the upper pole of the right kidney and multiple low-attenuation areas in the left kidney. 18 F-fluorodeoxyglucose (FDG)-PET/CT scan showed moderate FDG accumulation of cystic tumor in marginal lesion. In addition, FDG-PET/CT scan also showed moderate FDG accumulation in the pancreatic body. Laparoscopic right nephrectomy was performed. Histological examination was revealed lymphoplasmacytic infiltrate with focal fibrosis and severe narrowing or obstruction of lumen of collecting duct in renal medulla. Furthermore, the IgG4 positive plasma cells infiltrated exceeding 10 cells per one high-power field in renal medulla. The ratio of IgG4-plasma cells to IgG-positive plasma cells was about 50%. The serum level of IgG4 was also elevated (218 mg/dl). Based on these findings, we finally diagnosed IgG4-related tubulointerstitial nephritis with renal cystic change.
  
  
  CONCLUSIONS
  IgG4-related kidney disease might cause cystic formation by severe narrowing and obstruction of collecting duct.
authors.forename: Hideo
authors.initials: H
authors.lastname: Fukuhara
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Taniguchi
authors.forename: Manabu
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Naoto
authors.initials: N
authors.lastname: Kuroda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fukata
authors.affiliation: Department of Urology, Kochi Medical School, Kohasu, Oko, Nankoku, Kochi 783-8505, Japan. keiji@kochi-u.ac.jp.
authors.forename: Keiji
authors.initials: K
authors.lastname: Inoue
authors.forename: Shimpei
authors.initials: S
authors.lastname: Fujimoto
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Terada
authors.forename: Taro
authors.initials: T
authors.lastname: Shuin
mesh_terms: D002292:Carcinoma, Renal Cell / Q000175:diagnosis; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007074:Immunoglobulin G; D007150:Immunohistochemistry; D007668:Kidney / Q000000981:diagnostic imaging; D052177:Kidney Diseases, Cystic / Q000175:diagnosis / Q000276:immunology* / Q000473:pathology*; D007680:Kidney Neoplasms / Q000175:diagnosis; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000175:diagnosis / Q000276:immunology* / Q000473:pathology*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed
chemical_list: D007074:Immunoglobulin G; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18