Since 2011, a significantly higher frequency of the minor T allele of the MUC5B promoter polymorphism has also been demonstrated in patients with idiopathic non-specific interstitial pneumonia (iNSIP), rheumatoid arthritis associated-interstitial lung disease (RA-ILD), chronic hypersensitivity pneumonitis (cHP), asbestosis and interstitial lung abnormalities, but not in patients with systemic sclerosis associated-ILD (SSc-ILD), myositis-associated ILD, antisynthetase syndrome and sarcoidosis (1–9). Here, MUC5B is linked to rheumatoid arthritis.