S100A9 and idiopathic pulmonary fibrosis: S100A9 was not only identified as a marker for idiopathic pulmonary fibrosis (Hara et al., 2012; Yamashita et al., 2021), but also aggravated dermal fibrosis induced by bleomycin in mice via activation of ERK1/2 MAPK and NF-κB pathways (Xu et al., 2018).