In patients with acute HF, OPG levels were higher at baseline (n = 139), at day 2 (n = 103) and at discharge (n = 45) than in patients with non-HF related dyspnoea [7.8 (5.5–10.4) vs. 5.4 (3.8–7.2) pmol/L, p<0.001; 7.4 (5.3–8.6) vs. 5.6 (4.3–7.7) pmol/L, p<0.001; 8.7 (6.3–11.3) vs. 3.8 (5.2–6.9) pmol/L, p<0.001]. The gene discussed is TNFRSF11B; the disease is hydrops fetalis.