Abstract
Pulmonary involvement is common in rheumatoid arthritis (RA) and affects all the components of the lung. Interstitial lung disease (ILD) is the most predominant pulmonary manifestation and has been identified as the main cause of morbidity and mortality in RA. Clinically significant RA-ILD occurs in approximately 10% of RA patients. Several risk factors, such as old age, male gender, and smoking, have been reported to date. Histologically, the proportion of the usual interstitial pneumonia (UIP) pattern is higher in RA-ILD than in ILD associated with other connective tissue diseases, and RA-ILD also shows nonspecific interstitial pneumonia and organizing pneumonia patterns. High-resolution computed tomography scans are highly predictive of the histological UIP pattern with a specificity of 96%-100%. Acute exacerbation, which is the acute deterioration of the respiratory status characterized by newly developed bilateral infiltrates with unknown etiologies, has been reported in RA-ILD. Although acute exacerbation of RA-ILD has high mortality, similar to that of idiopathic pulmonary fibrosis, its incidence is lower in RA-ILD than in idiopathic pulmonary fibrosis. A consensus treatment has not yet been established. Current therapeutic regimens typically include corticosteroids with or without cytotoxic agents. Recent large longitudinal studies reported that the prognosis of RA-ILD was poor with a median survival of 2.6-3.0 years. Furthermore, histological and/or radiological patterns, such as UIP or non-UIP, have significant prognostic implications. RA-ILD patients with histological or radiological UIP patterns have poorer prognoses than those with non-UIP patterns. This review assessed the characteristics of RA-ILD by overviewing recent studies in the field and focused on the clinical significance of histological and/or radiological patterns in RA-ILD.