Dengue haemorrhagic fever complicated with intravascular haemolysis, coagulopathy and haemophagocytic lymphohistiocytosis: a case report

BACKGROUND: Dengue haemorrhagic fever (DHF) may occasionally manifest with atypical or severe complications under the umbrella of expanded dengue syndrome (EDS). Haemophagocytic lymphohistiocytosis (HLH) and intravascular haemolysis are rare but potentially fatal complications that require a high index of suspicion, particularly when clinical deterioration persists beyond the critical phase. CASE PRESENTATION: We report a previously healthy 19-year-old woman who presented with DHF and subsequently developed persistent fever, worsening transaminitis, rising bilirubin levels, haemoglobinuria, and progressive cytopaenia despite completion of the critical phase. Laboratory evaluation demonstrated markedly elevated ferritin (> 40,000 ng/mL), hypertriglyceridaemia, hypofibrinogenaemia, and features of intravascular haemolysis, including indirect hyperbilirubinaemia, reticulocytosis, elevated LDH and a negative direct antiglobulin test. Ultrasonography revealed new splenomegaly. Bone marrow aspirate confirmed haemophagocytosis. She met six HLH-2004 diagnostic criteria, supporting a diagnosis of secondary HLH triggered by acute dengue infection. The patient was treated with intravenous dexamethasone (10 mg/m²/day) for 14 days with tapering, alongside transfusion support, N-acetylcysteine, and cautious fluid management. She achieved full clinical and biochemical recovery. CONCLUSION: This case highlights a rare but severe manifestation of EDS where DHF was complicated by intravascular haemolysis and secondary HLH. Persistent fever, worsening liver dysfunction, cytopaenia or coagulopathy beyond the expected course of dengue should prompt early evaluation for HLH. Timely diagnosis and corticosteroid therapy can be lifesaving.