The ILD that is seen in patients with RA is very similar to the ILD that we see with other connective tissue diseases, although perhaps what differs from what we see in dermatomyositis or systemic sclerosis is that we can control RA-ILD to a better extent. RA-ILD is difficult to diagnose, assess, and manage. For patients with RA who are perhaps not as physically active as we would like, we might not even have an index of suspicion to ask the appropriate questions to uncover these types of symptoms. Overall, we know that patients with RA-ILD do not comprise a large group. Further, the ILD may not be as amenable to therapy, despite the fact that we are largely successful in treating the RA. Antifibrotic agents have been used in some cases of systemic sclerosis–related ILD, but it is unknown whether this would be beneficial in RA-ILD. The interleukin-6 (IL-6) inhibitor tocilizumab appeared to stabilize lung function (forced vital capacity), a secondary end point, in phase 2 and phase 3 trials in patients with systemic sclerosis, even though the primary end point (improvement in modified Rodnan Skin Score) was not met. Further, placebo-treated patients who were crossed over to tocilizumab also demonstrated a stabilization of forced vital capacity, suggesting a clear benefit of the therapy. Despite these results, the sponsor has chosen not to pursue the US Food and Drug Administration approval of tocilizumab for systemic sclerosis–related ILD. Nevertheless, we might still consider using an IL-6 inhibitor for a patient with RA-ILD, even if purely from the perspective of treating the RA.

Because the prevalence of RA-ILD is relatively low, obtaining baseline chest radiographs may not be necessary for all patients. However, for patients with RA with pulmonary symptoms, such as dyspnea upon exertion, a high-resolution computed tomography (CT) is appropriate to better assess for structural evidence of ILD.  

Another question that arises in patients with RA-ILD is whether their ILD is attributable to RA, to the medications used to treat RA, or to some other factor. Should certain medications be avoided when treating RA because of their associated potential risk for the development of ILD? For instance, should we avoid using methotrexate to treat RA in a patient with ILD? If the ILD is related to RA disease activity, then treatment with methotrexate might be expected to result in improvement in or stabilization of ILD. Thus, once ILD is diagnosed in a patient with RA, it is important to establish an objective quantitative measure of pulmonary function, such as the diffusing capacity for carbon monoxide, so that the patient’s ILD can be followed longitudinally and monitored closely for any worsening.

Patients who are at increased risk for RA-ILD include men, smokers, those who are strongly seropositive, and individuals who have respiratory symptoms. These may be the categories for whom high-resolution CT screening may be a good first step. However, patients with RA who do not have symptoms of ILD may, with some frequency, have radiologic findings suggestive of fibrosis, which can make management decisions challenging. RA and CT changes suggestive of fibrosis are much more prevalent than is progressive fibrotic lung disease in RA; fortunately, the latter group of patients is relatively small. Clinically significant RA-ILD is estimated to occur in only about 5% to 10% of patients with RA; however, much larger percentages have radiologic findings suggestive of ILD. So, it is important to pay attention to the clinical signs and symptoms of ILD and to then avoid therapies that may exacerbate the ILD. The presence of pulmonary hypertension is a potential complication in those with advanced disease, but it is more common in patients with systemic sclerosis. I would agree with Dr Strand that, for patients who have mild symptoms, drugs such as IL-6 inhibitors, rituximab, and abatacept all have anecdotal positive results from small studies. However, no biologic agent is approved for this indication. For those patients with the most severe forms of ILD, I generally refer them to an ILD specialist. This is a very fast-moving scientific niche, with significant investigational use of drugs that include antimetabolites and antifibrotic agents.