The activation of the ERK signaling pathway is associated with many pro-fibrotic cytokines and kinases, such as transforming growth factor-β (TGF-β), platelet-derived growth factor, matrix metalloproteinases, etc. The expression of activated ERK1/2 protein was up-regulated in human or animal models of PF (Liu et al., 2021). This evidence concerns the gene MAPK3 and pemphigus foliaceus.