MUC5B and rheumatoid arthritis: This was lower than the previous reported MAF of 34–38% in IPF, 33% in RA-ILD, 24–32% in cHP and 29% in asbestosis, but in the present study, subgroups with a reported prevalence of the MUC5B variant equal to the normal population (i.e., sarcoidosis, SSc-ILD, myositis-associated ILD and antisynthetase syndrome) were also included (1–5,7–9).