A Case Report of Severe Tick-borne Disease in a Young Infant: A Rare Trigger for Secondary Hemophagocytic Lymphohistiocytosis

Case DesCriptionA 2-month-old, full-term, previously healthy female with unremarkable prenatal history presented to the emergency introDuCtion Hemophagocytic lymphohistiocytosis (HLH) is a rare, lifethreatening condition characterized by a hyperinflammatory response due to immune dysregulation.It is characterized by uncontrolled activation of inflammatory mediators, primarily T-cells, NK cells, and macrophages. 1,2HLH is categorized into primary and secondary HLH.Primary HLH is thought to be due to genetic variants affecting the cytotoxic function of T-cells, NK cells, macrophage activation, and immune regulation. 1 In secondary HLH, immune dysregulation is triggered by an initial insult, such as malignancy, infection, or rheumatologic disorders.While viral infections, such as Epstein-Barr virus and adenovirus, are the most common infectious triggers for HLH, bacterial and fungal infections have also been reported to induce an exaggerated and uncontrolled inflammatory response, leading to secondary HLH. 1,3-5Among bacterial infections, tick-borne diseases have been reported in children to cause secondary HLH 6-8 but have not been seen in very young infants.We present the case of a 2-month-old female patient with secondary HLH due to severe Ehrlichia chaffeensis infection, who required extracorporeal life support for severe hemodynamic instability.