Frequency of Methotrexate Intolerance in Juvenile Idiopathic Arthritis Patients Using Methotrexate Intolerance Severity Score

Background: The Methotrexate Intolerance Severity Score (MISS) is a comprehensive scoring system used to assess methotrexate intolerance. Objective: The study aims to determine the frequency of methotrexate intolerance in JIA patients using MISS and its association with demographic factors, subtypes of JIA, duration of illness, and MTX intake. Methods: This cross-sectional study was conducted at the Department of Rheumatology, UCHS and The Children’s Hospital, Lahore. All patients having JIA and taking MTX for at least 3 months were enrolled. Demographic data, including age, gender, subtype of JIA, duration of the disease, and MTX dosage and duration, were collected. The MISS score has four elements: abdominal pain, nausea, vomiting, and behavioral symptoms. A cutoff value of 6 or above was considered indicative of MTX intolerance. Data was analyzed into SPSS version 22. Results: Out of 96 JIA patients, 60.4% were female and the mean age was 9.92 ± 4.11 years. Polyarticular seronegative JIA was present in 56.3% of patients. Among all patients, 22.9% had MTX intolerance according to the MISS score. Nausea was found in 58.3%, followed by behavioral symptoms in 44.8%. All MTX-intolerant patients experienced nausea and behavioral symptoms, with vomiting occurring in 59.1% and abdominal pain in 45.4%. MTX intolerance was significantly linked with increasing age in JIA patients but was not related to gender, subtype of JIA, duration of disease, and MTX intake, or MTX dose. Conclusion:  About one-third of all JIA patients were methotrexate intolerant having nausea and behavioral symptoms. MTX intolerance was significantly linked with increasing age in JIA patients taking MTX.