ACE2 and COVID-19: Being ACE2 the front door of SARS-CoV and SARS-CoV-2 (122, 123), it is at the crossroad between SARS-CoV-2 infection and COVID-19 pathogenesis, because in its double role as negative regulator of the RAS homeostasis, and as SARS-CoV-2 receptor, it plays a determinant function in the clinical evolution of COVID-19 patients.