title: Comparative clinical manifestations of IgG4- related and IgG4-negative primary tubulointerstitial nephritis.
abstract: OBJECTIVE
  To evaluate the prevalence of IgG4-related tubulointerstitial nephritis (TIN) and compare the clinical manifestations of IgG4-related and IgG4-negative primary TIN.
  
  
  METHODS
  Of 5,174 renal biopsies obtained between January 1996 and February 2010, 46 were positive for primary TIN without other kidney disease. Biopsy tissues were lost for 2 patients. The remaining 44 samples were assayed by immunoperoxidase staining with monoclonal mouse antibody to human IgG4.
  
  
  RESULTS
  Of the 44 patients with primary TIN, 12 (27%) were identified as IgG4+ plasma cells/HPF ≥ 10 and 32 (73%) as < 10. Estimated glomerular filtration rate (eGFR) was lower and proteinuria was higher in patients with IgG4+ plasma cells/ HPF ≥ 10 (p < 0.05). No other parameter such as age; gender distribution; incidence of hypertension, diabetes mellitus, drug history, pyuria; concentrations of hemoglobin and alkaline phosphatase; or kidney size differed significantly. Of the 44 patients with primary TIN, 25 (57%) were identified as IgG4-positive (IgG4+ plasma cells/HPF ≥ 1) and 19 (43%) as IgG4-negative. The two groups did not differ in age; gender distribution; incidence of hypertension, diabetes mellitus, drug history, pyuria, or proteinuria; concentrations of hemoglobin and alkaline phosphatase; eGFR; or kidney size. The improvement rate, however, was significantly higher in IgG4-positive than in IgG4-negative patients (p = 0.045). Of the 25 IgG4- positive and 19 IgG4-negative patients, 18 and 13, respectively, were treated, and 18 and 7, respectively, improved (p = 0.002). The median number of IgG4-positive plasma cells/HPF in the former group was 8 (range 1 - 90). The number of IgG4-positive plasma cells was significantly associated with the degree of proteinuria (r = 0.471, p = 0.018) and age (r = 0.529, p = 0.007).
  
  
  CONCLUSIONS
  Routine IgG4 staining is necessary in patients with primary TIN. Early treatment is also important in patients with IgG4-related primary TIN.
authors: Department of Nephrology, and Department of Pathology, Asan Medical Center, Seoul, South Korea.
authors: T Y
authors: TY
authors: Kim
authors: K S
authors: KS
authors: Park
authors: J S
authors: JS
authors: Choi
authors: S H
authors: SH
authors: Kang
authors: Y M
authors: YM
authors: Cho
authors: S B
authors: SB
authors: Kim
mesh_terms: D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000209:etiology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000150:complications* / Q000276:immunology; D010195:Pancreatitis / Q000209:etiology; D012189:Retrospective Studies
chemical_list: D000305:Adrenal Cortex Hormones; D007074:Immunoglobulin G