Potential pathogenesis and clinical aspects of pulmonary fibrosis associated with rheumatoid arthritis.

Pulmonary fibrosis is an extra-articular disorder that can occur in association with rheumatoid arthritis. The differential diagnosis of this disorder is similar to that of idiopathic pulmonary fibrosis, but specific entities such as atypical pulmonary infections and drug-induced interstitial lung disease must be considered as causes of pulmonary fibrosis in patients with rheumatoid arthritis. Although the cause of lung fibrosis in persons with rheumatoid arthritis is unknown, factors that can potentially contribute to the pathogenesis of this pulmonary disease include genetic susceptibility, development of an altered immunologic response, and/or aberrant host repair processes. The clinical course of patients with pulmonary fibrosis and rheumatoid arthritis is heterogeneous but is generally insidious, chronic, and progressive. These patients respond unpredictably to available empiric therapeutic agents and, overall, their prognosis is poor; limited data suggests that the median survival time can be less than 4 years.