Clinical characteristics and long-term outcomes of immune-complex membranoproliferative glomerulonephritis and C3 glomerulopathy in Japanese children

Abstract Background Membranoproliferative glomerulonephritis (MPGN) can be divided into immune-complex MPGN (IC-MPGN) and C3 glomerulopathy (C3G), which include dense deposit disease (DDD) and C3 glomerulonephritis (C3GN), respectively. These conditions result from abnormalities in different complement pathways and may lead to different prognoses. However, there are limited studies describing the respective clinical courses. Methods In this study, Japanese pediatric patients diagnosed with MPGN based on kidney biopsies conducted between February 2002 and December 2022 were reclassified as having IC-MPGN or C3G (DDD or C3GN). We retrospectively analyzed the clinical characteristics and outcomes of these patients. Results Out of 25 patients with MPGN, three (12.0%) were diagnosed with DDD, 20 (80.0%) with C3GN, and two (8.0%) with IC-MPGN. There were 13 (65.0%) patients and one (33.3%) patient in remission after treatment for C3GN and DDD, respectively, and no patients with IC-MPGN achieved remission. The median follow-up period was 5.3 (2.5-8.9) years, and none of the patients in either group progressed to an estimated glomerular filtration rate < 15 ml/min/1.73m2. Patients with C3GN presenting mild to moderate proteinuria (n=8) received a renin-angiotensin system inhibitor (RAS-I) alone, and these patients exhibited a significant decrease in the urinary protein creatinine ratio and a notable increase in serum C3 levels at the last follow-up. Conclusions The majority of patients with MPGN were diagnosed with C3GN. The remission rate for C3GN was high, and no patients developed kidney failure, indicating favorable outcomes. Additionally, it was suggested that patients with mild pediatric C3GN could be treated with RAS-I alone.