A nationwide survey of rapidly progressive glomerulonephritis in Japan: etiology, prognosis and treatment diversity

The etiology, prevalence, and prognosis of rapidly progressive glomerulonephritis (RPGN) including renal vasculitis vary among races and periods. To improve the prognosis of Japanese RPGN patients, we conducted a nationwide survey of RPGN in the nephrology departments of 351 tertiary hospitals, and found 1772 patients with RPGN (Group A: diagnosed between 1989 and 1998, 884 cases; Group B: diagnosed between 1999 and 2001, 321 cases; and Group C: diagnosed between 2002 and 2007, 567 cases). ANCA subclasses, renal biopsy findings, treatment, outcome and cause of death were recorded. The most frequent primary disease was renal-limited vasculitis (RLV) (42.1%); the second was microscopic polyangiitis (MPA) (19.4%); the third was anti-GBM-associated RPGN (6.1%). MPO-ANCA was positive in 88.1% of RLV patients and 91.8% of MPA patients. The proportion of primary renal diseases of RPGN was constant during those periods. The most frequent cause of death was infectious complications. The serum creatinine at presentation and the initial dose of oral prednisolone decreased significantly in Groups B and C compared to Group A. However, both patient and renal survival rates improved significantly in Groups B and C (survival rate after six months in Group A: 79.2%, Group B: 80.1%, and Group C: 86.1%. Six-month renal survival in Group A: 73.3%, Group B: 81.3%, and Group C: 81.8%). Early diagnosis was the most important factor for improving the prognosis of RPGN patients. To avoid early death due to opportunistic infection in older patients, a milder immunosuppressive treatment such as an initial oral prednisolone dose reduction with or without immunosuppressant is recommended.