[Familial hemophagocytic lymphohistiocytosis. Differential diagnosis with secondary hemophagocytic syndromes].

We report 2 cases of familial hemophagocytic lymphohistiocytosis in two children, hétérozygous twins, born from consanguine parents. This disease is characterised by disseminated lymphohistiocytic infiltrates with hemophagocytosis, that most commonly involves bone marrow, spleen, lymph nodes, liver and central nervous system. Differential diagnosis is difficult with infection-induced hemophagocytic syndromes. The only distinguishing feature in pathology is the expression of CD21, CD30 and CD35 antigens by histiocytes. Differenciation is made by an association of clinical and pathologic characteristics: a familial history, lack of infection or neoplasm, and immunohistochemical results. Diagnostic must be rapidly made, because this disease is always fatal without treatment.