title: Recognizing IgG4-related tubulointerstitial nephritis.
abstract: OBJECTIVE
  Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disorder affecting nearly all organs, including the kidney. Tubulointerstitial nephritis (IgG4-TIN) is the most common form of IgG4-related kidney disease (IgG4-RKD) and is the focus of this concise review.
  
  
  OBJECTIVE
  The study aims to describe when IgG4-TIN should be suspected and to summarize the diagnosis, treatment, and natural history of the disease.
  
  
  METHODS
  Ovid MEDLINE, Google Scholar, and PubMed were searched for full-text English language articles up to January 2016. References included in the manuscript were chosen at the authors' discretion based on their relevance to the subject of the review.
  
  
  RESULTS
  IgG4-TIN should be considered in patients presenting with abnormal urinalysis, abnormal kidney function, renal lesions on imaging, and elevated IgG, IgE, or hypocomplementemia. Diagnosis of IgG4-TIN requires a combination of histologic features (plasma cell-enriched TIN with >10 IgG4+ plasma cells/hpf, +/- TBM immune complex deposits in many cases) and at least one of the following:Characteristic radiologic findings (small peripheral low-attenuation cortical nodules, round or wedge-shaped lesions, or diffuse patchy involvement)Elevated serum IgG4 levelCharacteristic findings of IgG4-RD in other organs Other conditions such as lupus, vasculitis, diabetic nephropathy, and lymphoma must be excluded, as these can also present with IgG4+ plasma cells in the renal parenchyma. IgG4-TIN is generally responsive to steroids and B cell depletion with rituximab, but relapses are common and patients require close long-term follow-up.
  
  
  CONCLUSIONS
  Available data on IgG4-TIN are from retrospective observational studies.
  
  
  CONCLUSIONS
  IgG4-TIN is a distinct and emerging subtype of interstitial nephritis. Nephrologists must be aware of this entity and how to definitively diagnose and treat it. Prospective studies and ideally multi-center clinical trials are needed to study the epidemiology, treatment, and natural history of this disease.
authors.affiliation: Department of Medicine, University of British Columbia, 2775 Laurel Street, 10th Floor, Vancouver,, BC V5Z 1M9 Canada.
authors.forename: Shawna
authors.identifier: 0000-0003-0981-4417
authors.initials: S
authors.lastname: Mann
authors.affiliation: Department of Pathology and Laboratory Medicine, Providence Health Care, 1081 Burrard Street, Vancouver, BC V6Z 1Y6 Canada.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Seidman
authors.affiliation: Division of Nephrology, University of British Columbia, 2775 Laurel Street, 5th Floor, Vancouver, BC BC V5T 3A5 Canada.
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Barbour
authors.affiliation: Division of Nephrology, University of British Columbia, 1081 Burrard Street, Vancouver, BC V6Z 1Y6 Canada.
authors.forename: Adeera
authors.initials: A
authors.lastname: Levin
authors.affiliation: Division of Rheumatology, University of British Columbia, 839 West Broadway, Vancouver, BC V5Z 1J9 Canada.
authors.forename: Mollie
authors.initials: M
authors.lastname: Carruthers
authors.affiliation: Division of Hematology, University of British Columbia, 2775 Laurel Street, 10th Floor, Vancouver, BC V5Z 1M9 Canada.
authors.forename: Luke Y C
authors.initials: LY
authors.lastname: Chen
keywords: Autoimmune tubulointerstitial nephritis; Epidemiology; IgG4-related disease; IgG4-related kidney disease; IgG4-related tubulointerstitial nephritis; Tubulointerstitial nephritis