A genome-wide linkage study identified the mucin (MUC) 5B gene as associated with familial interstitial pneumonia and idiopathic pulmonary fibrosis (IPF) in a white population [8], while an association between the MUC4 gene and ILD induced by epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI) or acute exacerbation of IPF was reported in Japanese patients [9]. This evidence concerns the gene MUC5AC and idiopathic pulmonary fibrosis.