CD19 and Miyoshi myopathy: Boucher et al. [22] reported that CD19+CD34+ immature B cells and CD19+CD34− mature cells, but not CD19−CD34+ cells isolated from the BM of patients with MM showed colony formation activity and resistance to melphalan, lenalidomide, and bortezomib, indicating undifferentiated clonotypic B cells may represent MMSCs.