Demographic and clinical characteristics of rapidly progressive glomerulonephritis in renal vasculitis in the Japan renal biopsy registry

This study evaluated the clinical and demographic characteristics of biopsy-proven rapidly progressive glomerulonephritis (RPGN), with histological evidence of renal vasculitis. We focused on five vasculitis-related nephritides: MPO-ANCA, PR3-ANCA, anti-GBM, IgA vasculitis (IgAV), and lupus nephritis, —using data from the Japan Renal Biopsy Registry (J-RBR). Among the 35,870 native kidney biopsies, 2,285 (6.4%) were classified as RPGN. RPGN prevalence was highest in anti-GBM nephritis (90.4%), followed by MPO-ANCA (73.2%) and PR3-ANCA (53.5%). Age and sex distributions varied across diseases, with ANCA and anti-GBM nephritis predominantly affecting older adults, whereas IgAV and lupus nephritis were more common in younger populations. Severe proteinuria was frequent in all groups. The KDIGO risk classification revealed a high proportion of very high-risk cases of ANCA and anti-GBM nephritis, with age-related increases in IgAV and lupus nephritis. Patients with anti-GBM nephritis showed the lowest median estimated glomerular filtration rate, indicating severe renal impairment at the time of the diagnosis. RPGN cases mirrored these trends, with IgAV-RPGN patients skewed toward an older age. This registry-based analysis highlights the distinct clinical and demographic profiles of vasculitis-related RPGN and underscores the need for longitudinal studies to assess disease progression and outcomes.