Abstract: SA-PO0702
Fifteen Years in Hiding: DNAJB9-Positive Fibrillary Glomerulonephritis Emerging from the Shadow of Membranous Nephropathy
Session Information
- Glomerular Diseases: Complement-Mediated Glomerulopathies and Infection-Related GN
October 24, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- Iftikhar, Muhammad Ali, Loyola University Chicago, Chicago, Illinois, United States
- Andersen, Matthew R., Loyola University Chicago, Chicago, Illinois, United States
- Yousaf, Uzma, Loyola University Chicago, Chicago, Illinois, United States
- Abdulameer, Shahad, Loyola University Chicago, Chicago, Illinois, United States
- Picken, Maria M., Loyola University Chicago, Chicago, Illinois, United States
- Vellanki, Kavitha, Loyola University Chicago, Chicago, Illinois, United States
Introduction
Fibrillary glomerulonephritis (FGN) is a rare immune-complex glomerulonephritis comprising less than 1% of kidney biopsies, defined by Congo red-negative fibrils on electron microscopy and confirmed by DNAJB9 immunohistochemistry. FGN can mimic membranous nephropathy (MN) on light microscopy and immunofluorescence — a critical pitfall in the pre-DNAJB9 era. We report presumptive MN, stable for 15 years, unmasked on repeat biopsy as DNAJB9-positive FGN.
Case Description
A 56-year-old woman with presumptive MN (2010) had well-controlled proteinuria for over a decade. Urine protein-to-creatinine ratio rose from 1.9 g/g (January 2025) to 11.45 g/g (January 2026), prompting repeat biopsy in February 2026. Serum anti-PLA2R, hepatitis B, C, and HIV were negative. Kappa/lambda ratio 1.65; ANA low-titer positive (1:40). Light microscopy showed mesangial expansion; silver and Congo red stains negative. Immunofluorescence showed polyclonal IgG in mesangium and capillary walls. Electron microscopy confirmed haphazardly arranged fibrils in the mesangium and glomerular basement membrane (Image A). DNAJB9 immunohistochemistry was positive confirming FGN(Image B).
Discussion
This case carries three layers of novelty. First, all prior FGN-MN overlap reports describe simultaneous co-detection on a single biopsy — a 15-year interval between diagnoses is unprecedented. Second, the 2010 diagnosis predates DNAJB9 immunohistochemistry, raising the possibility that FGN was present from the outset, misidentified due to morphological overlap — a limitation now resolved by contemporary tools. Third, proteinuric relapse in PLA2R-negative stable MN warrants repeat biopsy rather than assumption of disease progression. DNAJB9-positive FGN can masquerade as MN for years; repeat biopsy remains the cornerstone when clinical trajectory deviates from expectation.