ACE2 and pemphigus foliaceus: Substantial evidence indicated that up-regulating the angiotensin (Ang)-converting enzyme (ACE)/AngII/ angiotensin II type 1 receptor(AT1R) axis could exacerbate PF, and that activation of angiotensin-converting enzyme 2 (ACE2) and generation of enzymatic product Ang-(1-7) could modify the intrapulmonary component of RAS (11).