[Macrophage activation syndrome in a patient with systemic juvenile idiopathic arthritis].

Machrophage activation syndrome (MAS) is a rare and potentially fatal disease, commonly associated with chronic rheumatic diseases, mainly juvenile idiopathic arthritis. It is included in the group of secondary forms of haemophagocytic syndrome, and other causes are lymphoproliferative diseases and infections. Its most important clinical and laboratorial manifestations are non-remitting fever, splenomegaly, bleeding, impairment of liver function, cytopenias, hypoalbuminemia, hypertriglyceridemia, hypofibrinogenemia and hyperferritinemia. The treatment needs to be started quickly, and the majority of cases have a good response with corticosteroids and cyclosporine. The Epstein-Barr virus is described as a possible trigger for many cases of MAS, especially in these patients in treatment with tumor necrosis factor (TNF) blockers. In these refractory cases, etoposide (VP16) should be administered, associated with corticosteroids and cyclosporine. Our objective is to describe a rare case of MAS probably due to EBV infection in a subject with systemic-onset juvenile idiopathic arthritis, which achieved complete remission of the disease after therapy guided by 2004-HLH protocol.