Drug treatment that increases survival and decreases HF decompensations and hospital admissions is suboptimally prescribed in HF patients with severe kidney function impairment, despite current strong evidence showing the benefits of many of these drugs (renin–angiotensin–aldosterone inhibitors, β-blockers, neprilysin inhibitors and mineralocorticoid receptor antagonists) [11,12,13,14], mainly due to concerns about renal function worsening and hyperkalemia [11,12]. The gene discussed is REN; the disease is hydrops fetalis.