Across 17 different BM cell types, we found that four (FCRLB, QPCT, SLAMF7 and TNFRSF17) of the five identified predictor proteins were expressed most abundantly in plasma cells (Extended Data Fig. 5 and Supplementary Table 12), suggesting these proteins may act as markers of plasma cell levels, which are elevated at primordial stages of MM development. The gene discussed is FCRLB; the disease is Miyoshi myopathy.