Attanasi M, et al. - This study was performed with 49 children with juvenile idiopathic arthritis (JIA) and 70 controls who do not show any respiratory involvement clinically after tested through spirometry, body plethysmography and lung diffusion for carbon monoxide (DLCO), analysed for the response of methotrexate (MTX) treatment. MTX effect was found dose dependent on lung function in children with JIA. The authors advocate a regular lung function test for such children preferably DLCO.