An unforeseen realityBlagotinšek Ošep, Anka (Avtor) Brecl, Eva (Avtor) Škerget, Matevž (Avtor) Savšek, Lina (Avtor) multiple sclerosisalemtuzumabhemophagocytic lymphohistiocytosisside effectsneuroimmunologydrug therapyadverse effectsAlemtuzumab is a humanized monoclonal antibody indicated for treatment of highly active relapsing-remitting multiple sclerosis (HA-RRMS). It binds to CD52 antigen and produces a rapid and prolonged lymphocyte depletion followed by a different pattern of T and B cell repopulation. Among others, its adverse events are autoimmune diseases. In this article, we present a patient with HA-RRMS, who was subsequently treated with alemtuzumab and afterwards developed hemophagocytic lymphohistiocytosis (HLH). Albeit rarely, HLH can be triggered by alemtuzumab treatment. HLH can favourably respond to prompt immunosuppressant therapy. Multidisciplinary approach by a team consisting of a neurology, hematology and rheumatology specialist is needed to treat this potentially lethal condition.20232023-08-09 15:35:13Članek v reviji148285sl