Juvenile dermatomyositis

Methotrexate (MTX) is the main corticosteroid-sparing drug used in JDM, having demonstrated superiority over cyclosporine (another immunosuppressive drug). In addition, a recent study by PRINTO (Paediatric Rheumatology International Organisation) has shown superiority in the use of MTX with corticosteroids over corticosteroids alone.

In JDM, subcutaneous use is recommended, at a dose of approximately 15 mg/m2 per week. During treatment with MTX, it is recommended to take folic acid to reduce some of the side effects. The most common guideline is to take 5 mg of folic acid orally 24 hours after the administration of MTX, but there are alternative guidelines such as the daily administration of 1 mg orally except on the day of the MTX dose, which are less commonly used in paediatrics as they are more uncomfortable for children.

During treatment, regular blood tests should be performed to monitor liver markers and haemogram (blood cells). An initial check-up is recommended 4-6 weeks after the start of treatment and should be repeated at least every 3 months thereafter. 

If any of the controls are altered and it is suspected that the cause of the alteration is MTX, depending on the degree of alteration, the frequency of the controls should be increased, the MTX dose should be reduced or MTX should be withdrawn.