Compared with pre-anti-BCMA TCE, CD138+ MM cells at relapse harbored a clonal 3-nucleotide deletion (TNFRSF17 c.98_100del, variant allele fraction (VAF) of 100% corrected for sample purity (45%) by allele-specific CN analysis of tumors (ASCAT) and Battenberg). The gene discussed is TNFRSF17; the disease is Miyoshi myopathy.