P0417THE ABSENCE OF C3 DEPOSIT IN MEMBRANOUS NEPHROPATHY IS ASSOCIATED WITH SPONTANEOUS REMISSION

Abstract

Abstract Background and Aims Membranous nephropathy (MN) is the most common cause of biopsied nephrotic syndrome in adults. Recently, it has been reported that the pathogenesis of MN may be associated with an activation of the complement system. The pathway of activation is not clearly established. The intensity of C3 deposition could be a good marker of this activation in MN as has been shown in other diseases (IgA nephropathy, crescentic GN). The aim of this study is to evaluate clinical-pathological data in a cohort of patients with MN and the significance of glomerular C3 staining as a possible predictor of renal outcomes. Method We analysed patients with idiopathic MN biopsied in our department between January 2000 and December 2019, excluding those who had no material for IF (n = 115). The patients were divided into positive (87 cases) and negative (28 cases) based on glomerular C3 deposition. We assessed the clinical and histological characteristics and the percentage of spontaneous remission (SR) and end-stage renal disease (ESRD). Results A total of 115 patients with MN were followed with a median follow-up of 65 (25-161) months. We found no differences in baseline characteristics between both groups, with the exception that patients with C3 deposit had less albumin at the time of biopsy that negative patients [2.4 (2-2.9) vs 2.8 (2.3-3.1) g/dl, P=0.011)]. Patients with C3-negative had a higher percentage of SR than patients with C3-positive (75 vs 24%, P = 0.000) and less need for immunosuppressive treatment (18 vs 56%, P =0.001). At the most recent follow-up, C3-positive group had higher creatinine [1.42 (0.8-1.7) vs 0.97 (0.71-1) mg/dl, P=0.045] and proteinuria [1.64 (0.08-3.2) vs. 0.62 (0.05-0.79) g / 24h, P = 0.039]. Regarding histology, we found no differences in glomerular sclerosis, tubular atrophy and interstitial fibrosis. The renal survival analysis showed no statistically significant differences between both groups (P = 0.091). We analysed a subgroup of patients (n = 23) with antibodies against the phospholipase receptor on blood at the time of the biopsy (13/23 were positive). 84% of this positive group presented C3-positive in the renal biopsy vs 25% of the C3-negative group (P =0.008). Conclusion Patients without C3 staining show a higher rate of SR and less need for immunosuppressive treatment than patients with C3-positive. These results would support the theory that complement activation in this entity can play an important role. It is possible that these patients with negative C3 deposit represent a MN with evolution to SR and in these patients and that these patients do not need immunosuppressive treatment.