Evaluation of Methotrexate Intolerance in Children With Morphea

Methotrexate is an immunosuppressant commonly used in dermatology. The prevalence of intolerance using the Methotrexate Intolerance Severity Score (MISS) in pediatric juvenile idiopathic arthritis (JIA) ranges from 25% to 75%, but studies in morphea patients are lacking. We sought to determine the prevalence and predictors of methotrexate intolerance in children with morphea compared with children with inflammatory skin diseases and JIA/uveitis.

Eligible patients were ages 2 to 18 years and were taking methotrexate for at least 3 months to treat morphea, inflammatory skin disease, or uveitis/JIA. Methotrexate intolerance was calculated using the MISS. A 1-way analysis of variance compared absolute intolerance scores. Multivariate regression analysis was used to compare MISS across diseases and covariates.

Of 48 participants (mean ± SD age, 11.3 ± 4.1 years, 70.8% female), 15 had morphea, 16 had JIA/uveitis, and 17 had inflammatory skin diseases. The overall prevalence of intolerance was 20.8%. Age, sex, duration, and dose did not correlate with overall MISS. The MISS mean ± SD total for oral dosing was 2.5 ± 3.4, compared with 6.78 ± 6.8 for subcutaneous dosing. Patients with JIA/uveitis had the highest prevalence of intolerance (37.5%, n = 6), followed by morphea patients (20%, n = 3) and inflammatory skin disease patients (5.9%, n = 1). The OR of intolerance according to route of administration was 11.2 (95% CI, 2.03-61.89).

Methotrexate intolerance was highest among patients with JIA/uveitis. The only predictor for risk of intolerance was subcutaneous route of administration. Future work could examine disease activity correlations and interventions designed to minimize intolerance.