As discussed above for non-COVID ARDS, low Ang II plasma levels, especially if they are lower than the Ang I levels, may be caused by reduced ACE activity or by increased processing of Ang II into Ang 1–7 by ACE2 (Krenn et al., 2020) or POP (Triposkiadis et al., 2021). This evidence concerns the gene ACE and acute respiratory distress syndrome.