To determine the clinical features of methotrexate (MTX) pneumonitis in patients treated for rheumatoid arthritis (RA).
The medical records of 284 patients with RA who had been treated with oral MTX (mean followup 33.2 mo) were reviewed retrospectively.
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).
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.