MUC5B and interstitial lung disease: Prevalence of RA-ILD shows high variability in the literature depending on the population, diagnostic methods and disease definitions used.13 Our lifetime risks compare well with previous estimates of clinically significant disease, reported to occur in up to 5%–10% of patients with RA.2–4 We show that the effect of MUC5B is similar in the population and in patients with RA, but as both MUC5B and RA are important risk factors of ILD, patients with RA who are MUC5B carriers are at a much higher risk of ILD than MUC5B carriers without RA.