Initial treatment patterns of primary membranoproliferative glomerulonephritis in Japan (2017–2021): an updated analysis based on nationwide personal clinical records

BACKGROUND: Primary membranoproliferative glomerulonephritis (MPGN) is a rare progressive kidney disease that often leads to end-stage kidney disease. Our previous nationwide registry study (Report 1, 2015-2018) characterized initial demographics and treatment patterns. In this study (Report 2), we aimed to update these findings, focusing on newly registered cases (2017-2021). METHODS: Personal clinical records of patients with primary MPGN between 2017 and 2021 were obtained from the national registry organized by the Japanese Ministry of Health, Labour and Welfare. Characteristics of primary MPGN throughout Japan were investigated. RESULTS: A total of 210 patients (median age, 49 years; male, 51%) with newly registered primary MPGN were identified. Nephrotic syndrome was present in 83.8% of patients at enrollment. Initial treatment frequently included corticosteroids (63.8%), with a modest increase in intravenous methylprednisolone pulse therapy (41.4%) compared with that in Report 1. The incidence of hemodialysis was 7.1%. Compared with those in Report 1, the demographic patterns were similar; however, nephrotic presentations were more common. Cyclosporine and mizoribine usage were significantly higher in the pediatric group (< 18 years, n = 44) compared to the corresponding usage in the older adult group (≥ 65 years, n = 75). The mean dosage of oral prednisolone and other immunosuppressants during initial treatment did not differ among the four age groups. CONCLUSION: Compared with the earlier report (Report 1), patients with newly registered primary MPGN presented with nephrotic syndrome more often, highlighting the continued risk of poor prognosis and the need for more refined therapeutic approaches.