Clinical features and pathogenesis of membranoproliferative glomerulonephritis: a nationwide analysis of the Japan renal biopsy registry from 2007 to 2015.

Background: The incidence and age distribution of membranoproliferative glomerulonephritis (MPGN) vary throughout the world by race and ethnicity. We sought to evaluate the clinical features, pathogenesis, and age distribution of MPGN among a large nationwide data from the Japan Renal Biopsy Registry (J-RBR).
Methods: A cross-sectional survey of 593 patients with MPGN (types I and III) registered in the J-RBR between 2007 and 2015 was conducted. Clinical parameters, and laboratory findings at diagnosis were compared between children (< 20 years), adults (20-64 years), and elderly patients (≥ 65 years).
Results: The median age of the patients was 59.0 years and mean proteinuria was 3.7 g/day. The rate of nephrotic syndrome was significantly higher in adults (40.4%) and elderly patients (54.0%) than in children (14.9%), whereas the rate of chronic glomerulonephritis was significantly higher in children (66.2%) than in adults (34.4%) and elderly patients (31.2%). According to the CGA risk classification, high-risk (red zone) cases accounted for 3.4% of children, 52.5% of adults and 84.1% of elderly patients with MPGN. As for pathogenesis, primary MPGN was most frequent (56.0%). Lupus nephritis was the most common disease among adult patients with secondary MPGN, whereas infectious disease was more common in elderly patients. Multiple regression analysis revealed that high systolic blood pressure and high proteinuria were independent factors associated with decreased estimated glomerular filtration rate (eGFR) in adults and elderly patients with MPGN.
Conclusions: In Japan, adults and elderly patients with MPGN had a lower eGFR and severer proteinuria than children.