HDAC9 and pemphigus foliaceus: In this review, we discuss the mechanism of action of HDAC and HDACi, the occurrence mechanism of PF, the potential mechanisms and functional differences of different HDAC subtypes and their inhibitors in PF, and discuss the key role of HDAC in mediating fibrosis regression, as well as the future research approaches of highly selective HDACi, in order to clarify the potential methods for precise targeting of PF treatment.