[Rheumatoid arthritis and lung - more than a minor aspect of the disease].

Although rheumatoid arthritis (RA) mainly manifests as polyarthritis, there is growing evidence that the initiation of the pathological immune reaction against citrullinated peptides takes place in the lung. However, in spite of this important role of the lung in pathophysiology, clinically manifest lung involvement has been demonstrated only in about 2-5 % of the patients with RA, and therefore is relatively rare. In particular the severe interstitial lung involvement with histological pattern of usual interstitial pneumonia has a bad prognosis and an increased mortality. Methotrexate (MTX), as the most important disease modifying drug for treatment of RA is not associated with the appearance or progression of interstitial lung disease in RA. MTX-induced pneumonitis is a rare, although potentially severe complication of this treatment.