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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

Rheumatology · UK scope · Sources checked 27 Aug 2026 · Clinical 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.
  • HLH-2004 supports diagnosis when five of eight features are present, but was developed for paediatric protocols; HScore estimates adult reactive-HLH probability but neither is a gold-standard rule-out test.
  • A very high ferritin supports the syndrome but is less specific in adults than children. Serial direction linked to blood counts, fibrinogen, triglycerides and organ function is more useful.
  • Bone-marrow haemophagocytosis may be absent early and occurs in sepsis, transfusion and critical illness; never delay treatment solely to repeat a negative marrow.
  • Search triggers in parallel: EBV and other infection, T/NK or B-cell lymphoma, leukaemia, Still disease, lupus, immunodeficiency, transplant and treatment-associated syndromes.
  • Rheumatic MAS commonly receives immediate high-dose glucocorticoid and early specialist anakinra; severe adult HLH often needs dexamethasone and etoposide tailored to trigger and organ function.
  • EBV-associated disease may require rituximab when infected B cells are implicated, but rituximab is an adjunct and does not replace T-cell-directed HLH control or lymphoma therapy.
  • Clinical improvement requires fever, haemodynamic, neurological, blood-count, fibrinogen, liver and ferritin recovery; a falling ferritin alone does not prove control.

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.

A steep ferritin rise accompanied by falling platelets, neutrophils or haemoglobin, rising triglycerides and falling fibrinogen is more concerning than any isolated threshold.

Bleeding, purpura, line ooze, prolonged clotting, low fibrinogen or rapidly rising D-dimer suggests consumptive coagulopathy and requires urgent blood-product and cause-specific planning.

Lymphadenopathy, splenomegaly, weight loss, night sweats, LDH rise, abnormal film or focal PET uptake raises lymphoma-associated HLH and makes protected marrow or tissue urgent.

Seizure, confusion, focal deficit, meningism or reduced consciousness can reflect CNS HLH, infection, metabolic failure or treatment toxicity and needs immediate neurological assessment.

A patient with Still disease, systemic JIA or lupus who develops disproportionate fever, cytopenia, hepatitis and coagulopathy may have MAS even when CRP remains high and ESR paradoxically falls.

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.

  1. Call haematology, critical care, infection and the relevant rheumatology or oncology team; stabilise airway, circulation, glucose, coagulation and failing organs.
  2. 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.
  3. Start credible antimicrobial coverage and agree an immediate immune-treatment threshold from trajectory, trigger and organ threat rather than waiting for every criterion.
Rheumatic MAS first-lineSuppress cytokine activation early

Still disease, systemic JIA or lupus phenotype dominates and organ-threatening MAS is probable.

  1. Give specialist IV methylprednisolone induction while covering credible infection and monitoring haemodynamics, glucose, mental state and coagulation.
  2. Add anakinra early for severe or inadequately responsive MAS, selecting SC or IV route and renal-adjusted interval through the commissioned protocol.
  3. Escalate with haematology if organ failure or laboratory trajectory persists because etoposide

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.Take cultures when feasible, treat infection concurrently, and monitor glucose, blood pressure, rhythm, mental state, gastrointestinal and fluid complications.
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.Use only within specialist protocol; screen and treat infection, adjust in major renal impairment, monitor neutrophils and liver tests, and recognise that high-dose and IV use are off-label.
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Sources and review status6 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

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.

  • ASH recommendations for management of HLH in adultsAdult probability, trigger investigation, dexamethasone, etoposide and escalation principles.
  • HLH-2004 diagnostic and therapeutic guidelineEight diagnostic criteria and the dexamethasone-etoposide protocol framework.
  • HScore development and validationAdult reactive-HLH probability variables and interpretation.
  • Intravenous anakinra in secondary HLHCritical-care rationale, specialist dosing approaches and safety considerations for severe secondary HLH.
  • Kineret European product informationAnakinra infection, neutrophil, renal and administration safety; high-dose and IV HLH use is off-label.
  • Dexamethasone UK product informationSystemic dexamethasone contraindications, infection, metabolic and taper safety.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewUnited Kingdom
Rheumatic MAS transition

Still or lupus activity becomes sustained fever, cytopenia, coagulopathy and hepatitis; ESR may fall as fibrinogen is consumed despite clinical deterioration.

Neurological involvement

Confusion, irritability, seizure, meningism or focal deficit can represent CNS inflammation, infection, haemorrhage or metabolic failure and changes immediate support.

-based HLH treatment may still be required.
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