CD38, a 45-kDa type II transmembrane glycoprotein without an internal signaling domain, is widely and uniformly expressed on MM cells and is also expressed at a relatively low level on normal lymphoid cells, myeloid cells, and other non-hematopoietic tissues, providing the rationale for its use as a clinical target in MM [24]. This evidence concerns the gene CD38 and Miyoshi myopathy.