MM is characterized by clonal proliferation of malignant PCs; therefore, we focused on profiling of PBs (PB/PC1–2 clusters; CD20–, CD27het, CD38+, CD45+, and CD138–) as precursor of PCs and mature PCs (PC1–7 clusters; CD19het, CD20het, CD27het, CD38+, CD45lo, and CD138+). The gene discussed is CD38; the disease is Miyoshi myopathy.