A single nucleotide polymorphism in the promoter region of the MUC5B gene has been linked to the development of familial interstitial pneumonia and sporadic idiopathic pulmonary fibrosis (Fingerlin et al., 2013; Noth et al., 2013; Seibold et al., 2011; Stock et al., 2013; Zhang et al., 2011) and it has been suggested that this polymorphism might be associated with overexpression of MUC5B in the lung. Here, MUC5B is linked to pulmonary fibrosis.