The prevalence of rheumatoid arthritis (RA)–associated interstitial lung disease (ILD) has been underrecognized despite it having a significant impact on patient morbidity and mortality. Current research efforts are focused on identifying biomarkers of ILD risk, screening protocols, and effective treatments.

Right now, the lung is generating interest in RA, with a significant number of abstracts and sessions focused on this topic at various professional conferences. ILD was first identified in patients with RA 40 or 50 years ago, but there was a lack of interest at that time, mainly because we were focused primarily on the joints. Over the last 10 years, there has been a growing appreciation that we have underrecognized the prevalence of ILD in patients with RA. An estimated 10% to 20% of patients with RA have indolent ILD, with usual interstitial pneumonia being very common. Progressive ILD is uncommon in individuals with RA, unlike scleroderma, but there is a small subset of patients who clearly have it.

We have been concerned about the impact of RA therapies on the lung, particularly methotrexate, as this agent can cause acute hypersensitivity pneumonitis. However, studies and large data sets have not demonstrated that methotrexate is a cause of ILD. We are searching for more biomarkers to identify patients with rheumatic diseases who are at risk for ILD. We do not routinely do pulmonary function testing or chest computed tomography (CT) scans in patients with RA. If we could identify clinical phenotypes of risk for ILD, we would go ahead and do pulmonary function tests and chest CT scans in patients with such phenotypes.

When patients with RA present with dyspnea or chronic cough, they may already have significant lung involvement. We are not advanced at identifying patients with ILD because, even though we know how to screen for the disease, we do not know when to screen. If ILD is suspected, however, we know to order pulmonary function tests, including the diffusing capacity of the lungs, and a high-resolution CT scan of the chest. If they show something, we send the patient to a pulmonologist, who then starts them on drug therapy, supplemental oxygen (if required), and pulmonary rehabilitation.

However, we do not know the best treatments for ILD in patients with RA because we are really in the infancy of this. We use drugs that are used for scleroderma-associated ILD. Mycophenolate has been used, but clinical trials have shown it to be ineffective for RA joint disease, so patients would still need other treatments for their joints. Rituximab has been used in uncontrolled settings, as has tocilizumab, which is US Food and Drug Administration (FDA) approved for scleroderma-associated ILD. Finally, antifibrotic drugs may slow the rate of progression, but tolerability is a problem.