ACE2 and pemphigus foliaceus: In this study, we hypothesized that QFHXD could play a protective role in PF by attenuating oxidative stress, possibly by modulating ACE/AngII/AT1R and ACE2/Ang-(1-7)/Mas axes, given the link between PF pathogenesis and oxidative stress and the ACE-AngII-AT1R/ACE2-Ang1-7-Mas axis.