COVID-19 development and progression consist of five major pathological mechanisms (Figure 5): (1) direct virus-induced cytotoxicity in ACE2-expressing cells; (2) dysregulation of the RAAS as a result of virus-mediated ACE2 downregulation; (3) dysregulation of immune responses; (4) endothelial cell injury and thrombo-inflammation; and (5) tissue fibrosis (Gupta et al., 2020). The gene discussed is ACE2; the disease is COVID-19.