A Case Report on CNS Hemophagocytic Lymphohistiocytosis in an Infant With Dengue Hemorrhagic Fever

India is an endemic country for dengue. The incidence of hemophagocytic lymphohistiocytosis (HLH) with dengue in children has been well-reported. However, central nervous system (CNS) HLH associated with dengue has not been described in the literature yet. We hereby report a novel case of CNS HLH triggered by dengue infection. An eight-month-old, well-grown male infant with uneventful antenatal, perinatal, and neonatal history was admitted with a history of febrile illness associated with cough, cold, vomiting, and loose motions and one episode of hematochezia and hepatosplenomegaly on examination. Investigations revealed bi-cytopenia, hyper-ferritinemia, deranged coagulation profile, liver function test, and hypo-fibrinogenemia. Dengue non-structural protein 1 ( NS1) antigen was positive. The child was given dexamethasone and continued supportive care with a diagnosis of dengue shock syndrome. The child showed an overall transient improvement, however, he had rebound fever followed by right focal convulsion on Day 9 of steroids. MRI brain revealed areas of diffusion-restricted embolic infarcts with diffuse leptomeningeal enhancement and mild cerebral edema, and CSF showed a total leukocyte count of 80 cells with 75% lymphocytic picture, histiocytes with hemophagocytosis, confirmatory of CNS HLH. Intrathecal methotrexate, hydrocortisone, and intravenous (IV) etoposide were started. However, the child succumbed to his illness. CNS involvement in dengue-triggered HLH needs to be suspected despite subtle neurological signs and aggressively managed following a multi-departmental approach to ensure the best clinical and neuro-developmental outcomes.