Interestingly, it has been published that MM patients displaying higher CD19 levels have a dismal outcome as compared with the CD19-negative patients, and expression of both CD19 and CD28 together with the absence of CD117 was hypothesized to be a marker of a MM stem cell, although there are conflicting reports as to the ability of CD19+ cells to form MM colonies in vitro [58,59]. This evidence concerns the gene CD28 and Miyoshi myopathy.