MUC5B and idiopathic pulmonary fibrosis: Particularly, the presence of a single nucleotide polymorphism (SNP) for the minor allele T of MUC5B, which is located at 3 kb upstream of the MUC5B gene transcription start site on 11p15 (rs35705950), has been described as the strongest risk factor to predispose to IPF both in sporadic and familial cases [53,54].