TNFRSF17 and Miyoshi myopathy: We evaluated soluble BCMA (sBCMA) level (produced predominantly by MM cells) in serum at different time points, and observed high levels before the first CAR T cell infusion, which dropped significantly to a very low level coincident with the clinical response; however, sBCMA remained low even at the time of relapse with increased burden of MM, indicating a lack of BCMA production by MM cells (Fig. 2B).