Practical Approach to the Evaluation and Management of Rheumatoid Arthritis-Interstitial Lung Disease Based on its Proven and Hypothetical Mechanisms.

The prevalence of interstitial lung disease in patients with rheumatoid arthritis varies from 10 to 42%. Rheumatoid arthritis patients with interstitial lung disease have three times the risk of death compared with those without the disease. Prognosis seems to be related to the high-resolution computed tomography pattern. Usual interstitial pneumonia pattern, resembling idiopathic pulmonary fibrosis, carries a worse prognosis. Validated strategies to identify different phenotypes and assess the disease activity in rheumatoid arthritis interstitial lung disease are lacking. However, the utilization of high-resolution computed tomography, composed disease activity scores, and anti-citrullinated peptide antibodies titers can help to guide decisions in clinical practice. Mechanisms involved in lung disease may be different from those implicated in joint involvement. This could explain why in a significant proportion of cases, interstitial lung disease does not improve or even worsens with standard therapies used successfully to treat the joint component (e.g. anti- umor necrosis factor agents). In this scenario, a group of drugs that targets the adaptive immune response (e.g. rituximab or abatacept) seems to target more specifically the process that takes place in the lungs. Moreover, the recent emergence of anti-fibrotic drugs, which have already proven effective in idiopathic pulmonary fibrosis, may provide an alternative treatment strategy in rheumatoid arthritis-usual interstitial pneumonia. In this review, we propose a practical approach to the evaluation and therapy of rheumatoid arthritis interstitial lung disease. Validation of strategies directed to assess the activity of lung disease and identify the underlying mechanisms are needed. Clinical trials evaluating a therapeutic approach with specific targets based on the disease phenotype are warranted.