Pre-Treatment Serum Complement 3 Levels And Rituximab Response In Idiopathic Membranous Nephropathy

Abstract

Objective: The efficacy of rituximab has been reported in patients with idiopathic membranous nephropathy (MN). We aimed to evaluate the relationship between biochemical tests at diagnosis, immunohistochemical profile, and rituximab response in patients with idiopathic MN unresponsive to other therapies in our center. Material and Methods: In this study, nine patients with idiopathic MN who received other immunosuppressive therapies between 2017-2022 and who underwent renal biopsy in our center were evaluated. Pre-treatment phospholipase A2 antibody levels were positive in 6 patients, and antibodies could not be analyzed in 3 patients. All patients received rituximab ≥2 grams after renin-angiotensin-aldosterone system (RAAS) blocker, cyclophosphamide, steroid, and calcineurin inhibitors. Results: Of the nine patients included in the study, 7 (78.2%) were male, and the mean age was 39.713.2 years. Four patients had complete remission (CR) with rituximab treatment, and five had partial remission (PR). Sclerotic glomeruli count, IgG, A, M, C1q, C3, C4d, fibrinogen, kappa and lambda staining, tubular atrophy, and interstitial fibrosis findings on renal biopsy were similar. However, the serum complement 3 (C3) level was significantly lower within normal limits (1.22  0.26 vs 1.560  0.56 p=0.016). The mean arterial pressure was significantly higher (96.22.5 mmHg vs 84.754.27 mmHg, p=0.018) in patients with partial remission compared to those with complete remission. Conclusion: A low baseline serum C3 level within normal limits before treatment in patients with idiopathic membranous nephropathy may help predicting unresponsiveness to other immunosuppressive therapies and partial response to rituximab treatment.