Serum mean concentration of OPG was 12.5 ± 11.5 (0.7–60.2) pmol/L in multiple myeloma patients and 6.4 ± 5.3 (0.7–17.4) pmol/L in healthy subjects (P < 0.03) (by Mann-Whitney test) (Figure 1). The gene discussed is TNFRSF11B; the disease is plasma cell myeloma.