Lung disease is the most frequent and among the most severe extra-articular manifestation of rheumatoid arthritis (RA). Several interesting advances have been made in recent years in our understanding of this respiratory disease.
1. The induction of BALT responsible for follicular lymphoid infiltrates has been demonstrated in the wall of respiratory bronchioles. These lymphoid infiltrates are similar to synovial and skin cellular infiltrates and secrete specific markers of RA (citrullinated proteins). These data strongly suggest a common pathogenic mechanism for RA in the joints and in other sites, such as the lung. 2. Improvements in high resolution computed tomography (HR- CT) increased the sensitivity of diagnosis. CT evidence of pulmonary disease is present in 50% of RA patients, but only 10% of these patients have clinical symptoms. The different lung manifestations, frequently combined, have been clearly described: pulmonary nodules (20%); small airways disease (30%): bronchiolitis, bronchiolectasis, and bronchiectasis; diffuse interstitial pneumonia of various types (20%). 3. Predictors of progression and therapeutic response remain unknown. Therefore treatment is empirical and based on usual indications and on drugs used in idiopathic fibrosis and other connective tissue pulmonary pathologies.
New biological drugs such as TNF blocking agents or anti CD20 antibody could be beneficial. Infections and drug-induced pneumonitis are not described in this review but must be considered systematically when an RA patient presents with lung involvement.