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While rheumatoid arthritis-associated interstitial lung disease (RA-ILD) has been known to be a serious extra-articular rheumatoid arthritis (RA) manifestation for decades, RA-ILD and other pulmonary sequelae of RA have been of intense interest in recent years. Patients with RA have excess respiratory mortality of RA compared with the general population.1 2 This respiratory burden of RA seems to be specific for patients with seropositive RA,1 and RA-ILD is likely a key contributor to the respiratory burden of RA. Median survival after clinical RA-ILD detection is poor, ranging from 3 years to 8 years in previous studies.3–5 Unlike nearly all other outcomes in RA, prevalence of RA-ILD does not seem to be decreasing over calendar time.5 This may be explained by several factors that include increased longevity of patients, improved articular disease activity unmasking symptoms of dyspnoea on exertion, increased awareness by clinicians of RA-ILD, greater ease in obtaining advanced chest imaging, or perhaps by medications used to treat RA-ILD. Thus, RA-ILD is a serious public health condition for patients with RA. Establishing the risk and identifying risk factors for RA-ILD are therefore of utmost importance. In Annals of the Rheumatic Diseases, Palomäki and colleagues investigate the lifetime risk of RA-ILD related to the MUC5B promoter variant.6
RA-ILD is a heterogeneous condition that is notoriously difficult to diagnose. Usual interstitial pneumonia (UIP) is the most common RA-ILD, considered to be fibrotic and progressive. A recent meta-analysis found that the UIP subtype had worse prognosis compared with other RA-ILD subtypes.7 Idiopathic pulmonary fibrosis (IPF) shares many of the same clinical and imaging features of UIP in RA-ILD. A common promoter variant of MUC5B (G>T at the rs35705950 single-nucleotide polymorphism) was identified as an important genetic risk factor for IPF.8 Subsequently, the MUC5B promoter variant …