Objective: To determine the clinical features of methotrexate (MTX) pneumonitis in patients treated for rheumatoid arthritis (RA).
Methods: The medical records of 284 patients with RA who had been treated with oral MTX (mean followup 33.2 mo) were reviewed retrospectively.
Results: MTX induced interstitial pneumonitis developed in 6 patients (2.1%). The affected patients were significantly older than those without MTX pneumonitis (67.3 +/- 9.8 vs 52.4 +/- 12.6 yrs, respectively; p < 0.005). The cumulative MTX dose ranged from 65 to 580 mg at the time pneumonitis developed. Five of the patients (83%) had preexisting interstitial abnormalities, while only 29 of the 278 patients without MTX pneumonitis (10%) had such abnormalities (p < 0.001). The frequency of adverse effects due to previous treatment with disease modifying antirheumatic drugs (DMARD) was 66.7% in MTX pneumonitis patients and 14.3% in the other 278 patients (p < 0.01).
Conclusion: Advanced age, preexisting interstitial abnormalities, and previous adverse reactions to DMARD may be associated with MTX pneumonitis. Patients with these characteristics require careful monitoring during MTX therapy.