Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive disorder that is indistinguishable from viral-associated hemophagocytic syndrome (VAHS). Both disorders are included in the broad category of hemophagocytic lymphohistiocytosis (class 2 histiocytosis).1 Familial hemophagocytic lymphohistiocytosis is a disease seen in infants and young children and the age of onset ranges from 1 day2 to 7 years,3 with more than 80% of cases presenting before age 2 years. It is usually fatal, with extensive brain involvement. Viral-associated hemophagocytic syndrome can occur in any age group, but is rare and patients usually recover. Diagnostic guidelines1 for hemophagocytic lymphohistiocytosis are fever (>7 days, >38.5°C), splenomegaly (>3 cm), cytopenia (>2 or 3 lineages in the peripheral blood and unassociated with a hypocellular or dysplastic marrow), hypertriglyceridemia [>2 mmol/L], and hypofibrinogenemia [<1.5 g/L]). Pathologically, hemophagocytic lymphohistiocytosis is in bone marrow, spleen, or lymph nodes with no evidence of malignancy. Histiocytes have morphologic immunophenotypic and ultrastructural features of normal sinus histiocytes4 and show prominent erythrophagocytosis. Clinically, patients with FHL present with fever, hepatosplenomegaly, pancytopenia, abnormal liver function test results, coagulopathies, and hypertriglyceridemia. Thirty percent of cases have shown neurologic abnormalities such as alteration of the level of conciousness, nuchal rigidity, seizures, and hemiparesis.5- 7 Major changes were meningeal, perivascular, and intraparenchymal lymphohistiocytic infiltrates.8 Erythophagocytosis was a variable finding.