MUC5B and pulmonary fibrosis: The gain-of-function variant of MUC5B promoter is an acknowledged risk factor for the development of IPF (Seibold et al., 2011), and one animal study also evidenced that selective overexpression of MUC5B in bronchoalveolar epithelial cells augmented bleomycin-induced lung fibrosis (Hancock, et al., 2018).