[Macrophage activation syndrome: a diagnostic challenge].

Macrophage activation syndrome, or hemophagocytic syndrome, is a rare disease with high morbidity and mortality. It is a disorder of the mononuclear phagocyte system. Two forms have been described; primary or familial hemophagocytic lymphohistiocytosis and secondary or sporadic hemophagocytic syndrome. Diagnosis of macrophage activation syndrome poses a real challenge for the pediatrician and in many cases is only made at autopsy. We describe two patients with hemophagocytic syndrome associated with parvovirus B19 and Epstein-Barr virus infection.