Therapeutic Challenges and New Era in Fibrillary Glomerulonephritis with the Introduction of DNAJB9: Experience from a Tertiary Nephrology Center

Background/ aim: Fibrillary glomerulonephritis (FGN) is a rare glomerular disease characterized by non-amyloid fibrillary deposits in the glomeruli, and positive staining for DNAJB9. We aimed to investigate the clinical, pathological characteristics and the outcomes of FGN patients from a tertiary nephrology center. Methods: Retrospective cohort study of eleven patients with a diagnosis of FGN between 2016 and 2025. Results: At diagnosis, nine patients had nephrotic-range proteinuria and eight patients had microscopic haematuria. The mean serum creatinine was 1.6 mg/dL and the mean proteinuria was 3.78 g/24h. In terms of comorbidities, one patient had systemic lupus erythematosus (SLE), one had sarcoidosis and one had lung cancer. Histologically, the most common pattern was a mesangial proliferative pattern, observed in six patients. DNAJB9 staining was performed in 5 patients and was strongly positive. 10 out of 11 patients were positive for both IgG immunofluorescence and C3. All patients received renin-angiotensin-aldosterone system blockade and immunosuppression. In 80% of patients, proteinuria was reduced by more than 50% with stable renal function. Partial remission was observed in 73% of patients with a median follow-up of 24 months. Conclusion: The disease is very heterogeneous and associated with co-morbidities. There is no standard therapy and outcomes are questionable.