MUC5B and rheumatoid arthritis: Genetic similarities regarding variant of the MUC5B promoter known to be a major risk factor for IPF have been found in RA-ILD: Juge et al. observed that this variant was more frequent in RA-ILD than in unaffected controls (adjusted odds ratio, 3.8; 95% CI, 2.8–5.2; p = 9.7 × 10–17) (38, 39).