An association between a functional polymorphism located in the putative promoter region of the MUC5B gene (rs35705950) and sporadic and familial IPF has been recently identified in 3 American cohorts including 916 patients [4], [5] and was recently confirmed in 2 genome wide association studies [6], [7]. This evidence concerns the gene MUC5B and idiopathic pulmonary fibrosis.