TNFRSF17 and Miyoshi myopathy: B cell maturation antigen (BCMA)–chimeric antigen receptor (CAR) T cell therapies [ciltacabtagene autoleucel (cilta-cel) and idecabtagene vicleucel (ide-cel)] (Berdeja et al. 2021, Munshi et al. 2021), first approved in 2021, have shown remarkable activity in very advanced refractory MM, and ide-cel is quickly becoming the preferred therapy for first relapse (San-Miguel et al. 2023).