Macrophage activation syndrome is a rare but a potentially fatal disease. This pathology is defined not only by clinical criteria (fever, splenomegaly), but also by biological criteria (bi or pancytopenia, hypofibrinogenemia, hypertriglyceridemia, hyperferritinemia) and cyto histological ones (hemophagocytosis in the bone marrow, in the spleen or in the peripheral lymph nodes). It may be primary or more often reactive to an infectious or a malignant pathology, an immune deficiency, or an autoimmune systemic disease. Its occurrence imposes a quite exhaustive etiological assessment, as the associated diseases are multiple. We report in this work the case of a patient in whom a macrophage activation syndrome secondary to a bacteraemia was diagnosed in the laboratory of Hematology of the Hassan II University Hospital -Fez, and whose evolution was marked by a good response to antibiotic therapy with a regression of clinical symptoms and an improvement of the biological parameters. However, the prognosis for macrophage activation syndrome remains severe with about 50% mortality in the literature. It is therefore considered as a serious condition, with a severe prognosis and a treatment that is still poorly codified.