Improved long-term prognosis of eosinophilic granulomatosis with polyangiitis: retrospective analysis of 87 patients after biologic therapy introduction in Japan.

Five-year survival in eosinophilic granulomatosis with polyangiitis (EGPA) exceeds 90%, but long-term prognosis is poor. We examined prognosis in 87 Japanese EGPA patients, seen between April 2018 and December 2024, after mepolizumab introduction. Primary outcomes were survival rate, relapse rate, and associated clinical factors. The 5-, 10-, and 20-year survival rates were 95.0%, 91.4%, and 85.2%, respectively. Nine patients died (mean age at death, 74.8 ± 6.6 years), with six deaths due to aspiration or bacterial pneumonia; none was due to active vasculitis. Older age at onset (p = 0.003) and BVAS at diagnosis (p = 0.011) were associated with poorer survival, but myocardial involvement (p = 0.43) and FFS2009 (p = 0.41) were not. Mepolizumab was administered to 69% of patients, many with cardiac involvement and frequent relapses (defined as disease occurrence at least once every 2 years after initial remission). Frequent relapses were associated with myocardial involvement (p = 0.021) and mepolizumab administration (p = 0.032). Long-term prognosis appeared favorable, with no deaths attributed to active vasculitis. Survival was comparable between the mepolizumab-treated and untreated groups, which included patients with severe and less severe disease, respectively; therefore, an independent effect of mepolizumab on prognosis could not be confirmed.