We measured lung function, in terms of lung volumes, forced expiratory flow-volume curves and diffusing capacity of carbon monoxide (DLCO), in a group of 61 patients with juvenile chronic arthritis (42 female; age range 5 to 33 years) to ascertain whether disease activity and treatment with low dose methotrexate (MTX) influenced these parameters. The whole population was divided into subgroups based on onset type (systemic, n = 27; pauciarticular, n = 12; polyarticular, n = 22), disease activity (active, n = 42; inactive, n = 19), and MTX treatment (treated, n = 27; not treated, n = 34).
We found that maximal-mid expiratory flow (MMEF) was significantly reduced in patients with active disease (p < 0.025). The mean DLCO value, expressed as a percentage of the predicted value, and DLCO corrected for the hemoglobin value were lower than expected (67% and 80%, respectively). Multiple regression analysis showed that the forced vital capacity (FVC), forced expiratory flow in one second (FEV1) and DLCO were all correlated to the clinical subtype of the disease (p < 0.05, p < 0.02, p < 0.02, respectively), and MMEF was related to disease activity (p < 0.025). There was no evidence of any effect of MTX treatment on the pulmonary parameters.
This study confirms that JCA is characterized by an impairment of lung function, mainly involving the small airways, and by interstitial damage. These changes are related to the clinical subtypes of the disease and to disease activity.