title: The incidence of IgG4-positive plasma cells staining TIN in patients with biopsy-proven tubulointerstitial nephritis.
abstract: OBJECTIVE
  IgG4 disease is rare. However, IgG4 tubulointerstitial nephritis (TIN) is the most common renal manifestation. IgG4 disease is usually associated with elevated serum IgG4 levels and other organ involvement, low-density renal lesions on enhanced CT imaging and immune activation. The incidence of IgG4-TIN may be underestimated, as staining for IgG4 is not routine. This study sought to describe the prevalence of previously undiagnosed IgG4-TIN. Due to the complexity of the diagnosis, we only attempt to look at IgG4-positive plasma cell TIN as a potential indication for IgG4 renal disease.
  
  
  METHODS
  A retrospective review of native renal biopsies performed between 2002 and 2012 with a primary diagnosis of TIN was selected. Samples for which interstitial nephritis was secondary to a glomerular disease were excluded. The tissues were stained for IgG4 and scored by two blinded observers. Demographic and follow-up details were collected. This study was approved by the local ethics committee.
  
  
  RESULTS
  82 cases of interstitial nephritis from a total of 1238 renal biopsies (2002-2012) were available after staining for further assessment. 12 samples demonstrated staining consistent with the criteria for IgG4-positive plasma cell TIN, of which 3 had mildly positive staining, 7 moderately positive staining and 2 had markedly positive staining. There were no statistically significant differences in the baseline characteristics between the positive and negative staining groups.
  
  
  CONCLUSIONS
  A number of cases of IgG4-positive plasma cell TIN were observed histologically that had been previously diagnosed as non-specific chronic TIN. IgG4-positive plasma cell TIN made up 1% of all renal biopsies performed over 10 years and 13% of all biopsies demonstrating TIN not related to glomerular disease. IgG4 staining should be considered routinely in biopsies demonstrating primary TIN.
authors: Renal Unit, Liverpool Hospital, Liverpool, NSW, Australia.
authors: Kathy
authors: K
authors: Mac
authors: Anatomical Pathology Department, Liverpool Hospital, Liverpool, NSW, Australia.|University of Western Sydney, Campbelltown, NSW, Australia.
authors: Xiao Juan
authors: XJ
authors: Wu
authors: Renal Unit, Liverpool Hospital, Liverpool, NSW, Australia.
authors: Jun
authors: J
authors: Mai
authors: Renal Unit, Liverpool Hospital, Liverpool, NSW, Australia.
authors: Kenneth
authors: K
authors: Howlin
authors: Renal Unit, Liverpool Hospital, Liverpool, NSW, Australia.|University of Western Sydney, Campbelltown, NSW, Australia.|University of New South Wales, Sydney, Australia.
authors: Michael
authors: M
authors: Suranyi
authors: Anatomical Pathology Department, Liverpool Hospital, Liverpool, NSW, Australia.|University of Western Sydney, Campbelltown, NSW, Australia.|University of New South Wales, Sydney, Australia.
authors: Jim
authors: J
authors: Yong
authors: Renal Unit, Liverpool Hospital, Liverpool, NSW, Australia.|University of Western Sydney, Campbelltown, NSW, Australia.|University of New South Wales, Sydney, Australia.
authors: Angela
authors: A
authors: Makris
mesh_terms: D000368:Aged; D001706:Biopsy; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D007684:Kidney Tubules / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000276:immunology* / Q000473:pathology; D010950:Plasma Cells / Q000378:metabolism* / Q000473:pathology; D012189:Retrospective Studies
chemical_list: D007074:Immunoglobulin G
keywords: HISTOPATHOLOGY; IMMUNOGLOBULIN; IMMUNOHISTOCHEMISTRY; KIDNEY