Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
Adult macrophage activation syndrome and secondary HLH
Essential points for quick revision.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Suspected hyperinflammatory multiorgan failure
Persistent fever with rapidly falling blood counts, rising ferritin, hepatitis, hypofibrinogenaemia, coagulopathy, shock, encephalopathy or organ failure can represent HLH or MAS and may deteriorate over hours; neither marrow haemophagocytosis nor completion of every criterion is required before escalation.
Action: Admit urgently under haematology with rheumatology, infection and critical-care input; obtain repeated HLH variables and cultures, PCR, imaging and malignancy samples in parallel; support failing organs and treat credible infection immediately; start syndrome- and trigger-appropriate immune therapy when clinical probability and trajectory are high rather than waiting for a single confirmatory test.
Synopsis
Recognise adult secondary haemophagocytic lymphohistiocytosis and rheumatic macrophage activation syndrome early, interpret imperfect criteria without delaying treatment, find infection, malignancy and inflammatory triggers in parallel, and escalate life-saving immune and organ support.
HLH is a time-critical hyperinflammatory syndrome, not a single test result; macrophage activation syndrome is the rheumatic-disease context of secondary HLH.
The key pattern is unremitting fever plus worsening cytopenias, liver injury, splenomegaly, hypertriglyceridaemia, falling fibrinogen, coagulopathy and a rapidly rising ferritin.
First-line action is simultaneous: stabilise organ failure, culture and treat infection, calculate evolving probability, protect marrow or node tissue, and discuss immune treatment immediately.
Key red flags
Persistent high fever with shock, hypoxaemia, encephalopathy, severe hepatitis, acute kidney injury or lactate rise requires immediate critical-care review and simultaneous sepsis and HLH treatment.
Dynamic laboratory constellation
Falling platelets and neutrophils with rising ferritin, AST and triglycerides and falling fibrinogen is a high-risk evolving signature even before five HLH-2004 criteria are complete.
Investigation priorities
01
Immediate repeated HLH panelFirst step
Measure syndrome trajectory and organ threat.
Management branches
Emergency first hourTreat physiology, infection and hyperinflammation in parallel
Persistent fever combines with cytopenia, coagulopathy, hepatitis, shock or neurological decline.
Call haematology, critical care, infection and the relevant rheumatology or oncology team; stabilise airway, circulation, glucose, coagulation and failing organs.
Send the complete repeated HLH panel, cultures and viral PCR and protect marrow, blood and accessible tissue samples without allowing sampling to postpone life-saving care.
Rheumatic MAS first-lineSuppress cytokine activation early
Still disease, systemic JIA or lupus phenotype dominates and organ-threatening MAS is probable.
Key medicines
Methylprednisolone intravenous pulseFor organ-threatening rheumatic MAS, a common specialist regimen is 500–1000 mg intravenously once daily for three days, followed by an oral glucocorticoid plan.
AnakinraA specialist severe-MAS regimen commonly starts 100 mg subcutaneously or intravenously every six to twelve hours, then adjusts dose and interval to response, body size and renal clearance.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.