Among 165 064 beneficiaries diagnosed with systolic HF, 121 164 (73.4%) were prescribed β-blockers and 107 363 (65.5%) were prescribed an angiotensin-converting enzyme inhibitor, angiotensin II receptor blocker, or angiotensin receptor–neprilysin inhibitor; of these beneficiaries, 105 955 (87.5%) and 94 253 (87.8%) had no medication copayment. The gene discussed is MME; the disease is hydrops fetalis.