Macrophage Activation Syndrome in Systemic Juvenile Idiopathic Arthritis

Abstract

One of the complications of systemic juvenile idiopathic arthritis (SJIA) is macrophage activation syndrome (MAS), which may be considered as a form of secondary haemophagocytic lymphohistiocytosis. Trigger factors are drugs (aspirin, nonsteroidal anti-inflammatory drugs, gold preparations, methotrexate, and tumour necrosis factor blocking agents), drug change, drug side effects, or initiation of biological drugs and infections. The pathogenesis of MAS is still unclear and it may be explained by uncontrolled activities of macrophages. A lot of proinflammatory cytokines such as tumour necrosis factor-α, interleukin (IL)-1, IL-6, and interferon gamma play important roles in the pathogenesis of MAS. The diagnosis of MAS is often challenging. In 2016, the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) approved classification criteria for MAS complicating SJIA. Corticosteroid and cyclosporin A treatment have been used in the treatment of MAS. Intravenous immunoglobulin treatment has been used in some cases of MAS. Biologic agents have been used, such as anakinra (IL-1 alpha and beta inhibition), canakinumab (IL-1 beta inhibition), and tocilizumab (IL-6 inhibition). Early detection and early intervention are vital to avoid poor outcomes in MAS. SJIA is a subtype of juvenile idiopathic arthritis, and MAS is a serious, potentially fatal, complication of SJIA that occurs most commonly in children.