Hemophagocytic lymphohistiocytosis associated with ocrelizumab treatment in a patient with multiple sclerosis

Background: Hemophagocytic lymphohistiocytosis (HLH) is a rarely recognized hyperinflammatory condition of high death risk. Objective: The objective was to describe a case of HLH in a patient with multiple sclerosis (MS) treated with ocrelizumab Methods: Clinical observation, laboratory testing, and use of HLH-2004 criteria for HLH diagnosis. Results: A 32-year-old Caucasian female developed HLH during ocrelizumab treatment. She met six of the eight HLH criteria including fever, splenomegaly, cytopenia, hypertriglyceridemia and hypofibrinogenemia, high serum ferritin level, and low natural killer (NK) cells. Conclusion: HLH should be considered in the differential diagnosis in MS patients displaying a fever and malaise syndrome following administration of ocrelizumab.