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Haemophagocytic Lymphohistiocytosis — RACP Adult Medicine MCQ

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HardHaematologyHaemophagocytic LymphohistiocytosisRACP Adult Medicine

A 35-year-old man with a history of ulcerative colitis on azathioprine develops a high fever and pancytopaenia (WCC 0.8 × 10⁹/L, Hb 78 g/L, platelets 35 × 10⁹/L). EBV PCR is strongly positive. What is the most likely diagnosis?

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Correct answer: E — EBV-associated haemophagocytic lymphohistiocytosis (HLH)

Immunosuppressed patients on azathioprine (particularly those with IBD who are EBV-seronegative at the time of starting immunosuppression) are at risk of EBV-triggered HLH. HLH presents with fever, pancytopaenia, hyperferritinaemia (often >10,000 µg/L), hypertriglyceridaemia, hepatosplenomegaly, and elevated soluble IL-2 receptor. Bone marrow may show haemophagocytosis. H-Score aids diagnosis. Treatment includes etoposide-based protocols and cessation of immunosuppression.

Reference: eTG – 2025 – Haematology; Histiocyte Society – 2004 – HLH-2004 Protocol