We measured respiratory parameters in children with juvenile idiopathic arthritis (JIA) without clinical signs of respiratory involvement and assessed the influence of methotrexate (MTX) treatment and disease activity on lung function.
In 49 JIA children and 70 controls lung volumes by spirometry and body plethysmography, and lung diffusion for carbon monoxide (DLCO) with single-breath technique were evaluated.
DLCO was significantly different between JIA children and controls (P = .01), whereas no differences were found in flow expiratory volume in 1 second (FEV 
In JIA children MTX treatment seems to have a dose-dependent effect on lung function. For this reason in these patients, a regular assessment of lung function, especially with DLCO evaluation, is recommended.