[Lymphohistiocytic activation syndrome (LHAS)].

Lymphohistiocytic activation syndrome (LHAS) is related to inappropriate stimulation of macrophage cells in bone marrow and lymphoid system. LHAS combines the non-specific clinical signs (fever, poor general condition, hepatosplenomegaly, lymphadenopathy) and suggestive biological elements (bi-or pancytopenia, abnormal liver function, coagulopathy, increased LDH, ferritin and triglycerides). The diagnosis of SALH remains an emergency every clinician should discuss before any febrile cytopenia. The etiology of LHAS is still obscure, but recent advances in the genetic study of familial forms provide some essential elements in understanding.