According to the hypotheses formulated on the origin and evolution of MM, the myelomatous precursors, which putatively are pre-B cells with clonogenic properties (CD19+, CD38+ and CD56+), circulate throughout the bone marrow and penetrate the vascular endothelium by anchoring to specific adhesion molecules that belong to the integrin family (ICAM-1, ICAM-2, VCAM and JAMs) [42,43,44]. The gene discussed is CD19; the disease is Miyoshi myopathy.