Macrophage activation syndrome in malaria.

Macrophage activation syndrome (MAS) is a clinical syndrome caused by an excessive proliferation of T lymphocytes and well-differentiated macrophages; an entity distinct from malignant histiocytosis. Although rheumatologic conditions are the common cause of MAS, a wide range of infections are also seen to cause MAS. We report an adolescent with severe Plasmodium falciparum malaria and MAS. He fulfilled six out of eight criteria required to diagnose hemophagocytic lymphohistiocytosis.