#1500 Clinical, histological characteristics, and evolution of fibrillary glomerulonephritis in a Spanish Cohort

Abstract Background and Aims Fibrillary glomerulopathy is a rare glomerulonephritis defined by the presence of medium-sized fibrils (15–20 nm), randomly arranged and usually Congo red negative. Its diagnosis requires the use of electron microscopy. It has been associated with multiple secondary causes, although in most cases, no association with another disease is found. To date, several series have shown the characteristics and progression of this disease. Our purpose is, following the work of other research groups, to describe the clinical and histological characteristics, as well as the progression of fibrillary glomerulopathy in a cohort of patients in Spain. Method A retrospective, single-center study describing the clinical, histological characteristics, progression, and response to treatment of fibrillary glomerulopathy in the province of Málaga between 2007 and 2023. Results 21 patients were diagnosed with fibrillary glomerulopathy through electron microscopy. Table 1 summarizes the baseline characteristics. The most common presentation was nephrotic syndrome (14, 66%). 10 (47%) patients had microhematuria at the time of diagnosis. Table 2 shows the values for serum creatinine, glomerular filtration rate, and protein/creatinine ratio at diagnosis and at the end of follow-up. No differences were found when comparing these parameters. In 4 patients, coexisting causes were identified (1 monoclonal gammopathy, 1 hepatitis C virus, 1 HIV, and 1 Sjögren's syndrome). 3 patients tested positive for DNAJB9 in the renal biopsy. Regarding histological characteristics, the most observed histological pattern was mesangial expansion (11, 55%), followed by the membranoproliferative pattern (6, 30%). 18 (94%) patients had low C3 levels in the biopsy, and the most identified light chain was lambda. 14 (66%) patients received only antiproteinuric (supportive) treatment, and 6 (28%) patients additionally received immunosuppressive (IS) treatment. All but one in the group that received IS treatment progressed to end-stage renal disease (ESRD), compared to 9 in the supportive group, without showing statistically significant differences (P = 0.3). The median time to the need for renal replacement therapy was 2 ± 3.75 years. After 5 years of follow-up, almost 70% had lost renal function. 8 (38%) patients underwent kidney transplantation. Any of them have showed recurrence of the disease. Conclusion In our court the use of immunosuppression is comparable to supportive treatment in terms of renal response. Transplanted patients have not shown recurrence of the disease.