[Macrophage activation syndrome complicating family lymphohistiocytosis].

Macrophage activation syndrome (MAS) is an anatomoclinic entity due to inappropriate macrophage activation. It is a rare pathology, characterized by clinical signs that are not very specific and by biological elements. Their association must evoke the diagnosis. It can be classified as primary or secondary, its prognosis is still unclear. We report the case of a 3-year and 4-month-old infant admitted to our department with primary MAS in order to remind clinicians the importance of suspecting primary cause in specific situations.