Fibrillary glomerulonephritis: Lessons from anti-CD20 therapy and repeat biopsy.

Fibrillary glomerulonephritis (FGN) is characterized by a severe renal prognosis. There is not uniformity of consensus regarding therapeutic treatment. Several reports on the effectiveness of rituximab have been published, but showed different rate of renal response. This paper aims to evaluate the clinical and histological effects of two rituximab-based regimens in fibrillary glomerulonephritis. Twenty-one patients with diagnosis of FGN managed in a single Center (1996-2023), were identified. Seventeen patients, since 2010, were treated with anti-CD20 antibodies and included in the present study. Eleven patients were treated with Rituximab monotherapy (Group 1), 6 with the Intensive B-cell depletion therapy protocol (IBCDT) (Group 2) which consists of the combination of low-dose rituximab, IV cyclophosphamide and steroids. At baseline mean serum creatinine and proteinuria were 2.0 mg/dL and 3.7 g/day respectively. In group 1, four patients achieved a response; in group 2, five out of 6 patients achieved a response (p = 0.0064). Responder patients had a percentage of sclerotic glomeruli ≤ 40. Eight patients underwent a second biopsy due to recurrence or failure to respond to prior therapy line. The present study confirms that FGN is primarily a B cell-driven disease and provides evidence that FGN can be effectively managed by achieving a profound depletion of CD20 + B lymphocytes; the disease is highly progressive and probably requires prolonged maintenance treatment, and lastly early diagnosis is critical for long-term outcome because a significant glomerular sclerosis at the time of the first biopsy precludes the possibility of reversing or stabilizing the course of the disease.