Impact of frailty on prognosis in elderly patients with organ-threatening ANCA-associated vasculitis. - Taito K; Hashimoto S; Fukushima K; Ogawa K; Yatabe K; Izawa A; Ohta Y; Matsuno S; Oka M; Suzuki N; Takei T; Itabashi M (Clinical and experimental nephrology, 2026)