Objective. - To assess changes in growth parameters associated with the response to methotrexate (MTX) therapy in pre-pubertal children with juvenile idiopathic arthritis (JIA) and who had not been treated with steroids.

Methods. - We enrolled 27 pre-pubertal children with JIA who had been treated with MTX but not with steroids. The children were considered to have responded to treatment if the number of joints with active disease decreased by at least 50% 1 year after treatment initiation. We compared growth parameters (height, growth rate, weight and body mass index (BMI)) in responders and non-responders.

Results. - Twenty-one children (77.8%) responded to MTX therapy. The growth parameters were similar in the responders and non-responders before the onset of treatment. After 1 year, height (P=0.025), growth rate (P=0.03), weight (P=0.007) and BMI (P=0.05) increased significantly in the responder group, but not in the non-responder group. This increase was maintained for growth rate and weight after 2 and 3 years of treatment. After 1 year, height (P=0.023) and growth rate (P=0.0009) were significantly higher in the responders than in the non-responders, and these differences were still significant after 3 years (P=0.01 and P=0.033, respectively).

Conclusion. - In pre-pubertal children with JIA, a clinical response to MTX therapy is associated with a significant increase in growth parameters.