Objectives: Methotrexate may cause severe adverse pulmonary side-effects in adults with rheumatoid arthritis. Our aim was to examine the long-term effect of MTX on lung function in patients with juvenile idiopathic arthritis (JIA).
Methods: We retrospectively reviewed the charts of all 68 patients with JIA treated with MTX at our centre over a 14-year period. Results of annual pulmonary function tests (PFT) were compared using paired t-tests adjusted by Bonferroni correction and by linear regression analysis.
Results: The patients in our study had taken MTX for a median of 6.7 years with a median cumulative dose of 3219 mg. In a subgroup of 37 patients PFT had been performed before the onset of MTX. In this subgroup there was a significant decrease of mean mid-expiratory flow (MMEF) after 3 years (-14.0%, p<0.001) of MTX. Diffusion capacity of the lung for carbon monoxide (DLCO) was reduced after the third year (-12.4%, p=0.001). In the total group there was a decrease in MMEF between years 3 and 4 after MTX onset (-13.5%, p=0.001). Forced expiratory volume (FEV1) showed a slight rise between years 4 and 5 (+5.5%, p=0.003). All other parameters remained without significant changes. There was no correlation of PFT results and cumulative MTX dose or JIA subtype. None of our patients developed clinically relevant lung disease.
Conclusions: In summary we found some declines of MMEF and DLCO during long-term treatment with MTX. Overall our data confirm the relative safety of long-term MTX treatment in patients with JIA. We conclude that further data on the development of pulmonary function in patients receiving MTX therapy would be helpful.