While a significant decrease in ACE2 activity was observed in human pulmonary arterial hypertension (PAH) patients (Hemnes et al., 2018), ACE2 knockout mice display worsened lung function, increased vascular permeability, enhanced lung edema, and neutrophil accumulation, attributed to a downregulation of ACE2 (Imai et al., 2005). The gene discussed is ACE2; the disease is pulmonary arterial hypertension.