TNFRSF17 and Miyoshi myopathy: B-cell maturation antigen (BCMA/CD269), which belongs to TNF receptor superfamily member 17 (5), is highly selectively expressed on the surface of MM cells, as the ideal target of majority targeted agents studied currently for the patients with MM (6), such as anti-BCMA mAbs, antibody-drug conjugates (ADCs), bispecific T-cell engagers (BiTEs), and BCMA-targeted adoptive cell therapy like chimeric antigen receptor (CAR)-T cell (Figure 1).