SP181COMPARISON OF VARIOUS FEATURES AND OUTCOMES IN ADULT PATIENTS WITH IMMUNE COMPLEX MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS AND C3 GLOMERULOPATHY

INTRODUCTION: C3 glomerulopathy (C3G), a recently described disease, encompasses glomerulonephritis (GN) with exclusive C3 deposition and absence or inadequacy of immunoglobulins in kidney biopsies. Since a considerable number of patients with C3G were diagnosed as primary membranoproliferative GN (MPGN) before the introduction of C3G as a different entity, we aimed to evaluate and compare clinical, laboratory, histopathological features and treatment responses of immune complex MPGN (IC-MPGN) and C3G. METHODS: Twenty patients with IC-MPGN and 15 with C3G, who were followed-up for a duration of 68 (IQR: 23-97) months, were enrolled in this retrospective study. Biopsy samples were evaluated by a nephropathologist, who was blinded to all clinical data. Primary outcome was defined as ≥50% reduction in baseline eGFR or development of stage 5 chronic kidney disease (eGFR <15 ml/min/1.73 m2). Secondary outcomes were complete (CR) or partial remission (PR). CR was described as a proteinuria level of <0.5 g/24h and an eGFR of ≥60 ml/min/1.73 m2 (or a return of ±15% of baseline values in those with eGFR <60 ml/min/1.73 m2). PR was defined as a proteinuria reduction of >50% (and a proteinuria level of <3 g/24h in patients with nephrotic-range proteinuria at baseline) and stabilization (±25%) or improvement in renal function. Associations of demographic, clinical, laboratory and histopathological characteristics of patients with study outcomes were analyzed, as well. RESULTS: Demographic, clinical, laboratory and histopathological features at the time of diagnosis are summarized in the table. Biopsy specimens contained a median of 17 (13-22) glomeruli. All patients were treated using ACEi/ARBs and corticosteroids. Mycophenolic acid derivatives were administered in 10 (50%) and 11 (73.3%) patients with IC-MPGN and C3G, respectively (p=0.163). Patients with refractory disease were treated with biological agents: Rituximab was administered in 5 (25%) and 3 (20%) cases with IC-MPGN and C3G, respectively (p=0.727); while eculizumab was used in only 2 patients (13.3%) with C3G. Overall 6 patients (17.1%) reached primary outcome [3 (15%) with IC-MPGN and 3 (20%) with C3G; p=0.698]. CR was seen in 14 patients (40%) [7 (35%) with IC-MPGN and 7 (46.6%) with C3G], while only 5 patients (25%) in MPGN group went into PR (p=0.112). Kaplan-Meier analysis revealed that renal survival rates were 85% and 80% in IC-MPGN and C3G groups, respectively (p=0.800) (Figure). In multivariate Cox regression analysis, only hemoglobin [p=0.046, HR: 0.750 (0.566-0.995)] and basal eGFR levels [p=0.011, HR: 0.981 (0.967-0.996)] were predictors of complete or partial remission. CONCLUSIONS: There is a significant similarity between patients with IC-MPGN and C3G in terms of not only clinical and laboratory features, but also renal survival rates and treatment responses.