Constitutively elevated levels of P-glycoprotein (CD243), ABC transporter, were detected in most PBs and PC subsets (related to a worse PFS in PC4), including all stages of MM B cell lymphopoiesis across all MM cohorts; however, no change or even a slight downregulation of breast cancer resistance protein (CD338) has been observed (37). This evidence concerns the gene ABCG2 and Miyoshi myopathy.