Rituximab Therapy for Fibrillary Glomerulonephritis in an Older Adult With Advanced Chronic Kidney Disease.

Fibrillary glomerulonephritis (FGN) is a rare immune-mediated glomerular disease characterized by progressive kidney dysfunction, proteinuria, and a high risk of progression to end-stage kidney disease (ESKD). No standardized treatment exists, although rituximab has emerged as a promising therapeutic option in selected patients. We report the case of a 75-year-old woman who presented with progressive kidney dysfunction and worsening proteinuria. Kidney biopsy demonstrated FGN with substantial chronic histologic injury. She was treated with two doses of rituximab 1 g administered intravenously two weeks apart, in conjunction with renin-angiotensin-aldosterone system (RAAS) blockade. Despite a baseline estimated glomerular filtration rate (eGFR) below 30 mL/min/1.73 m² and significant chronicity on biopsy, she experienced improvement and subsequent stabilization of kidney function, with a reduction in proteinuria. This case adds to the growing evidence supporting rituximab as a therapeutic option for selected patients with FGN, even in the presence of advanced chronic kidney disease.