14/11/2025
HLH (Hemophagocytic Lymphohistiocytosis)
A syndrome of uncontrolled, hyper-inflammatory immune activation.
Diagnostic Framework (HLH-2004 criteria — ≥5/8):
1. Fever
2. Splenomegaly
3. Cytopenias (≥2 lineages)
4. Hypertriglyceridaemia and/or hypofibrinogenaemia
5. Haemophagocytosis (marrow/spleen/LN)
6. Low/absent NK cell activity
7. Ferritin ≥500 ng/mL (usually >3,000–10,000 in HLH)
8. Elevated soluble IL-2 receptor (sCD25)
Typical Lab Pattern
Ferritin extremely high (often >10,000)
Fibrinogen low
Triglycerides very high
Transaminases can be markedly elevated
Hyponatraemia common
Treatment
Treat triggers (infection, malignancy, rheum disease)
Immunosuppression: dexamethasone ± etoposide (HLH-94/HLH-2004), anakinra increasingly used
ICU support
