Hemophagocytic Lymphohistiocytosis Triggered by Acute Dengue Infection in a Young Adult: A Case Report From the United Arab Emirates.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome characterized by uncontrolled immune activation and cytokine storm. Dengue, a flavivirus transmitted by Aedes mosquitoes, is usually self-limiting but may rarely trigger secondary HLH. Persistent fever accompanied by cytopenias, extreme hyperferritinemia, transaminitis, and hypofibrinogenemia should raise suspicion for this diagnosis. Although dengue is not endemic to the United Arab Emirates, a significant outbreak followed unprecedented rainfall and flooding in April 2024, resulting in a surge in imported and locally acquired cases and posing diagnostic challenges for hyperinflammatory conditions such as HLH. We report the case of a 22-year-old male admitted with acute dengue infection complicated by secondary HLH, diagnosed based on extreme hyperferritinemia, bicytopenia, marked transaminitis, and hypofibrinogenemia despite normal triglyceride levels. Early recognition and prompt initiation of corticosteroid therapy led to rapid clinical and biochemical improvement, preventing progression to a full-blown cytokine storm and the need for intensive care admission. This case underscores the importance of maintaining a high index of suspicion for HLH in dengue patients presenting with persistent fever and disproportionate inflammatory markers, particularly in young adults, even in non-endemic regions.