Clinical efficacy and safety data for the treatment of MM/RR MM (relapsed/refractory MM) with BCMA CAR T cells are good, with high response rates and low incidence of adverse events, but a series of lethal toxic reactions (e.g., cytokine release syndrome (CRS), neurotoxicity, graft versus host disease, and chronic renal failure) in some patients due to the escape of MM cells caused by reduced BCMA expression or loss of shedding are still inevitable (26–28). The gene discussed is TNFRSF17; the disease is Miyoshi myopathy.