Methotrexate as a possible trigger of macrophage activation syndrome in systemic juvenile idiopathic arthritis

Macrophage activation syndrome (MAS) is a potentially life threatening comp lication of chronic: rheumatic diseases, particularly systemic juvenile idi opathic arthritis (JIA). A number of triggers have been related to the deve lopment of MAS, including viral infections, nonsteroidal antiinflammatory d rug therapy, and gold salt injections. We describe a patient with systemic JIA who developed MAS shortly after receiving methotrexate. suggesting that this drug can be regarded as a potential trigger of MAS in children with J IA.