Hemophagocytic syndrome following alemtuzumab treatment for multiple sclerosis: A case report

•Alemtuzumab is used for treating relapsing-remitting multiple sclerosis.•Alemtuzumab produces a prolonged lymphocyte depletion with deferred t cell reconstitution.•This late repopulation of t cells favors the risk of autoimmune diseases.•Hemophagocytic syndrome could be one of this adverse events.•Hemophagocytic syndrome can lead to a severe progressive multi-organ failure.