Interstitial pneumonitis complicating rheumatoid arthritis. Sustained remission with azathioprine therapy.

A patient with classic rheumatoid arthritis developed biopsy-proven diffuse interstitial pulmonary fibrosis and ventilatory insufficiency which appeared to be irreversible. The administration of azathioprine coincided with significant immediate improvement in pulmonary function and clinical status. During five years of continuous azathioprine therapy, progressive improvement in lung function has been accompanied by marked deterioration of the rheumatoid joint disease, suggesting that the pulmonary and joint lesions of rheumatoid disease may not be mediated by the same pathways.