MUC5B and idiopathic pulmonary fibrosis: Genome-wide association studies have identified 20 independent single nucleotide polymorphisms (SNPs) that are associated with IPF risk to date.2, 3, 4 A single common SNP in the MUC5B gene promoter region (rs35705950) has a large effect on IPF risk with each copy of the T allele that is associated with a 4- to 5-fold increased risk of IPF.4