P030 Impact of methotrexate on growth in children with Juvenile Idiopathic Arthritis
Authors: Fazaa A , Rouatbi F , Miladi S , Ouenniche K , Souabni L , Kassab S , Chekili S , Ben Abdelghani K , Laatar A 
Published: November 2021

Abstract

Background
Juvenile idiopathic arthritis (JIA) is a heterogeneous group of chronic inflammatory disease which could be responsible for functional impairment and severe growth disturbance. Conventional disease-modifying antirheumatic drugs, such as methotrexate (MTX), may improve growth velocity especially by regulating systemic inflammation. The objective of this study was to evaluate the effect of MTX on growth parameters in pre-pubertal children with JIA and to determine the factors affecting the growth velocity.

Methods
We assessed height and changes in the height standard deviation score (SDS) at disease onset, at the onset of MTX and at the last follow-up visit in a cross-sectional study of JIA children. All patients were pre-pubertal when MTX began and were followed for at least 6 months afterward. We compared growth parameters (height, growth rate, weight and body mass index (BMI)) in responders and non-responders to MTX. The growth rate was defined as the number of millimeters of height acquired during 1 year. Associations between changes in the height SDS and discrete variables were evaluated using χ2 or Fisher’s exact tests. The significance level was set at 0.05.

Results
We enrolled 36 pre-pubertal children with JIA (34 boys and 12 girls) who had been treated with MTX orally. Median patient age was 6.2 years [4–13] at the onset of MTX and 8.4 years [6.1–14.9] at the latest follow-up. The median disease duration was 2.7 years [2.5–5.3]. Twenty-one patients (58.3%) had oligoarticular JIA, 2 patients (5.5%) had systemic JIA, 10 (27.7%) had polyarticular JIA and 3 (8.3%) had enthesitis-related arthritis. Nineteen children (52.7%) had received corticosteroids during an average period of 1.7 years [0.6–3] with a mean of 10 mg/day of prednisone or equivalent. The median duration of MTX at the latest follow-up was 3.1 years [0.62–5.5] with a mean MTX dose of 10 mg/m2/week [10–15]. Twenty-eight patients responded to MTX treatment and 8 did not. There were no significant differences between the responders and non-responders for age at treatment initiation, disease duration and mean MTX dose. At MTX onset, no significant differences between the two groups in terms of height (P = 0.52), growth rate (P = 0.08), weight (P = 0.74) and BMI (P = 0.9) were found. One year after MTX therapy, mean height (0.2 vs -1.1; P = 0.03), mean growth rate (0.5 vs –2.9 SDS; P = 0.01), mean weight (0.4 vs -2.3 SDS; P = 0.01) and mean BMI (0.6 vs -1.9; P = 0.04) were significantly higher in the responder group than in non responders, respectively. At the latest follow-up, this increase was significantly maintained for growth rate (P = 0.001) and height (P = 0.002) in the responder group. In the multivariate analysis, patients who required &gt;10 mg/m2/week of MTX, systemic JIA and patients with reliance on steroids had a significantly lower growth velocity after the onset of MTX (P &lt; 001, P = 0.02, P = 0.02 respectively).

Conclusion
In our study, the increase in growth parameters in pre-pubertal children with JIA was associated with a better control of the disease activity under MTX therapy.