Dynamic hematologic recovery patterns to guide clinical differentiation along the dengue-hemophagocytic lymphohistiocytosis hyperinflammatory spectrum: A case report.

Dengue infection may trigger a hyperinflammatory response that closely resembles secondary hemophagocytic lymphohistiocytosis (HLH), making therapeutic decision-making particularly challenging in patients who fulfill multiple HLH-associated diagnostic criteria. Distinguishing self-limited dengue-associated immune activation from progressive HLH requiring immunomodulatory therapy remains an important clinical dilemma. We report a 19-year-old woman presenting with prolonged fever, pancytopenia, hepatosplenomegaly, marked hyperferritinemia, hypofibrinogenemia, hypertriglyceridemia, elevated soluble interleukin-2 receptor levels, and a high HScore, initially raising strong suspicion for secondary HLH. Bone marrow examination demonstrated mildly hypocellular marrow without overt hemophagocytosis; however, this finding was interpreted in conjunction with the overall clinical course rather than as an exclusion criterion for HLH. Despite fulfilling several HLH-associated parameters, the patient remained clinically stable and demonstrated spontaneous defervescence, progressive reticulocyte recovery, rapid platelet rebound, and a marked decline in ferritin levels during supportive treatment alone, resulting in complete clinical and hematologic recovery without corticosteroids or HLH-directed therapy. This case illustrates that dynamic longitudinal assessment may provide greater clinical value than isolated diagnostic thresholds when evaluating dengue-associated hyperinflammation. Integrating recovery trajectories with overall clinical stability may assist clinicians in identifying patients who can be safely observed while facilitating timely recognition of those who develop progressive immune dysregulation requiring HLH-directed treatment.