The randomized double‐blind trial EXACT‐HF (Xanthine Oxidase Inhibition for Hyperuricaemic Heart Failure Patients), which followed up a group of 128 HF with reduced ejection fraction patients treated with 600 mg of allopurinol for 24 weeks, did not prove any effect on mortality and/or deterioration of HF when compared to the control group. The gene discussed is XDH; the disease is hydrops fetalis.