OPG concentrations were significantly lower in patients with RAD (median 0.16 ng/mL; IQR 0.11, 0.22) compared with non-RAD (median 0.19 ng/mL; IQR 0.12, 0.28) (ORadj 0.20 per ng/mL increase; 95% CI 0.05, 0.80; p = 0.02). The gene discussed is TNFRSF11B; the disease is dyschromatosis symmetrica hereditaria.