The phenotypic initial and subsequent heterogeneity of the MM clone, especially CD45 heterogeneity which is the most important one, demonstrates the existence of a competition between subclones for limited resources (that are mainly nutrients/growth factors like IL6 and IGF1 whose effects on MM cells are discriminated by the presence or absence of CD45 on MM cells) from the microenvironment (exerting selection pressures), then selection of the most aggressive clones (68, 69, 70). The gene discussed is IGF1; the disease is Miyoshi myopathy.