Etanercept in the treatment of macrophage activation syndrome.

Macrophage activation syndrome (MAS), a recognized complication of systemic juvenile rheumatoid arthritis (sJRA), has been associated with significant morbidity and mortality. Dysregulation of macrophage-lymphocyte interactions leading to uncontrolled proliferation of highly activated macrophages and massive release of proinflammatory cytokines including tumor necrosis factor-alpha (TNF-alpha) appears to be central to the pathogenesis of this syndrome. Until now the mainstay of therapy has been corticosteroids and cyclosporin A. We describe a patient with MAS and sJRA successfully treated with the anti-TNF agent etanercept. The outcome in this patient suggests etanercept might be an effective therapeutic agent in MAS.