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Kidney Week

Abstract: TH-PO541

IgG Subclass Switch in Fibrillary Glomerulonephritis: Possible Natural History of the Disease

Session Information

  • Pathology and Lab Medicine
    November 03, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
    Abstract Time: 10:00 AM - 12:00 PM

Category: Pathology and Lab Medicine

  • 1700 Pathology and Lab Medicine

Authors

  • Biederman, Laura, The Ohio State University, Columbus, Ohio, United States
  • Ibrahim, Dalia Y., The Ohio State University, Columbus, Ohio, United States
  • Satoskar, Anjali A., The Ohio State University, Columbus, Ohio, United States
  • Nadasdy, Tibor, The Ohio State University, Columbus, Ohio, United States
  • Brodsky, Sergey V., The Ohio State University, Columbus, Ohio, United States
Background

Fibrillary glomerulonephritis (FGN) is an uncommon glomerular disease characterized by non-periodic fibrillar deposits of immunoglobulins usually positive for polyclonal IgG. Staining for IgG subclasses routinely performed and is usually dominant for IgG4. However, the natural history of this disease is not well documented.

Methods

Kidney biopsies with FGN were identified in a renal pathology database at Ohio State Wexner Medical Center from 12/1/2006 to 3/1/2022, when routine IgG subclass staining was performed. A total of 164 cases with IgG subclass data were reviewed, and seven patients with a diagnosis of FGN who had both an original diagnostic kidney biopsy and a follow up kidney biopsy were identified.

Results

A total of 164 cases of FGN were identified since 12/2006 with IgG subclass staining. Of those, 39 were dominant for IgG1, 67 were dominant for IgG4, and 58 had co-dominant staining for IgG1 and IgG4. Among these, a total of 7 patients had a repeat biopsy after their initial diagnosis. Of these 7, at initial biopsy, 71% of the patients with repeat biopsy showed dominant subclass staining for IgG4, with the remaining showing dominant staining for IgG1 alone or IgG1 and IgG2 . Two patients showed IgG subclass switching, both from IgG4 dominance to IgG1, and both were biopsied at more than 4 years after the initial diagnosis. Of the 5 patients with repeat biopsies who did not show subclass switching, 2 had repeat biopsies at 1 year or less, 2 had repeat biopsies between 1 and 5 years after initial diagnosis, and 1 had a repeat biopsy at 9 years or more. The other patient biopsied at more than 9 years showed IgG1 dominance on both the initial and subsequent biopsies.

Conclusion

FGN is an uncommon disease with a poorly understood natural history. Changes in IgG subclass staining from IgG4 to IgG1 may be part or the natural history of the disease.

  Initial Biopsy SubclassSubsequent Biopsy SubclassYears after initial diagnosis
Patient 1IgG4 and IgG1IgG14
Patient 2IgG4 and IgG1IgG1>10
Patient 3IgG4 and IgG1IgG4 and IgG13
Patient 4IgG1IgG19
Patient 5IgG1 and IgG2IgG1 and IgG23
Patient 6IgG4 and IgG1IgG4 and IgG1<1
Patient 7IgG4 and IgG1IgG4 and IgG1<1