Although RA is defined as a symmetrical inflammatory arthropathy, a wide variety of extra-articular manifestations are seen in patients with RA. The pleuropulmonary manifestations of RA encompass airway diseases (eg bronchiolitis obliterans), pleural diseases (eg pleuritis with or without effusion) and parenchymal pulmonary diseases [1, 2]. Interstitial lung disease (ILD) is associated with RA (RA-ILD), but the prevalence, incidence and natural history are not well defined. The prevalence of ILD in RA depends on the population selected for study (mild vs severe disease) and the methods applied for its detection (clinical, physiological, radiological or pathological). The paper by Koduri et al.[3] in this issue of Rheumatology sheds light on the incidence and the natural history of RA-ILD.

They report the results from an RA inception cohort, the Early Rheumatoid Arthritis Study (ERAS)[3]. Using a prospective, observational, longitudinal study design, extra-articular features and comorbidity were recorded annually in a well-established inception cohort of RA with 20-year follow-up. Patients with clinically significant pulmonary conditions were further investigated as part of standard clinical practice, which included plain radiology, pulmonary function tests and high-resolution CT (HRCT) scan if RA-ILD was suspected; however, none of the patients had lung biopsy. Fifty-two of 1460 (3%) patients with RA developed RA-ILD: half of them either at baseline or within 3 years of onset, indicating that RA-ILD is an early feature of RA. The incidence of RA-ILD was 4/1000 per year and increased with advancing age and disease severity or activity (as measured by the HAQ). Importantly, 39 of the patients with RA-ILD died (mainly due to respiratory insufficiency, which was the primary cause of death). Median survival following the diagnosis of RA-ILD was only 3 years. This cohort study clearly shows that RA-ILD is an important feature of RA and has a poor prognosis, which is an important message that is clinically relevant.