Macrophage activation syndrome secondary to dengue in a pediatric patient

Abstract

Macrophage activation syndrome (MAS) is a secondary form of hemophagocytic lymphohistiocytosis (HLH) associated with severe hyperinflammatory states and constitutes a rare but potentially fatal complication of dengue in children. We present the case of a 3-year-old female patient, previously healthy and without underlying immunodeficiencies, from Casanare (Colombia), with acute dengue infection confirmed by NS1 antigen and reactive IgM. The patient presented with persistent fever beyond the critical phase, progressive severe pancytopenia, hyperferritinemia, hypertriglyceridemia, and splenomegaly. Given suspicion of HLH, intravenous immunoglobulin (2 g/kg) was promptly administered, resulting in rapid resolution of fever, hemodynamic stabilization, and sustained recovery of hematologic and hepatic parameters. This case highlights the need to consider MAS in the setting of persistent fever and progressive cytopenias associated with dengue, enabling early immunomodulatory intervention.