Co-culture of BCMA/TACI-directed CAR T cells with patient-derived MM samples induced significant target cell toxicity on human MM cell lines in vitro even in the presence of soluble BCMA, TACI, or APRIL, except for the highest dose of soluble BCMA tested at 1000 ng/mL, in addition to significant IFN-γ release in comparison to control CAR T culture. The gene discussed is IFNG; the disease is Miyoshi myopathy.