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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.

Acquired coagulation-factor inhibitors

Haematology and transfusion · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Acquired haemophilia with major bleeding

Rapid soft-tissue, retroperitoneal, gastrointestinal, genitourinary, postpartum or postoperative bleeding with an isolated prolonged APTT can cause shock, compartment injury or airway compromise despite no previous bleeding disorder.

Action: Use ABCDE and anatomical haemorrhage control, contact a haemophilia centre immediately, send mixing studies, factor VIII and inhibitor samples without delaying haemostasis, avoid invasive procedures where possible, and begin centre-directed recombinant factor VIIa, activated prothrombin-complex concentrate or recombinant porcine factor VIII for clinically relevant bleeding.

Synopsis

Recognise acquired haemophilia and other factor inhibitors from unexpected bleeding and mixing-test patterns, achieve urgent haemostasis, and eradicate the inhibitor while limiting treatment-related infection and thrombosis.

  • Suspect acquired haemophilia A in new extensive bruising, soft-tissue, mucosal, postpartum or postoperative bleeding with no lifelong history and an isolated prolonged APTT.
  • First-line laboratory assessment is FBC, PT, APTT, fibrinogen, thrombin time, medicine and sample review, followed urgently by immediate and incubated mixing, factor VIII activity and Nijmegen Bethesda inhibitor titre.
  • A mixing study that fails to correct after incubation supports a time-dependent inhibitor, but anticoagulants and lupus anticoagulant can confound it; interpret with the specialist laboratory.
  • Clinical bleeding severity, site and haemoglobin trajectory determine treatment urgency; inhibitor titre and factor VIII level do not reliably predict how severely a patient will bleed.
  • Preferred haemostatic options for significant acquired haemophilia bleeding are recombinant activated factor VII, activated prothrombin-complex concentrate or recombinant porcine factor VIII, selected by expertise and monitoring capability.
  • Recombinant factor VIIa is commonly 90 micrograms/kg intravenously every 2–3 hours initially; activated PCC is 50–100 units/kg every 8–12 hours, never exceeding 200 units/kg/day.
  • Begin inhibitor-eradication therapy promptly after diagnosis, but individualise corticosteroid alone versus combination treatment because frailty and infection risk can outweigh faster remission.
  • Minimise venepuncture and invasive procedures, avoid intramuscular injections, monitor haemoglobin and bleed sites closely, and reassess need for VTE prophylaxis as factor VIII recovers.

Key red flags

Falling haemoglobin, hypotension, severe abdominal, back or groin pain, nerve deficit or tense swelling suggests concealed retroperitoneal or muscle haemorrhage and requires urgent imaging after haemostasis begins.

Postpartum bruising or bleeding with an isolated prolonged APTT may be acquired haemophilia even when delivery was initially uncomplicated and previous haemostasis was normal.

A new prolonged APTT must not be dismissed as lupus anticoagulant when the patient is bleeding; factor deficiency, heparin contamination and a time-dependent inhibitor require urgent distinction.

Investigation priorities

01
First-line: FBC, PT, APTT, fibrinogen and thrombin timeFirst stepFirst line

Define the bleeding consequence and localise the laboratory defect while detecting DIC or anticoagulant contamination.

Management branches

New isolated prolonged APTTExclude drug before inhibitor

A bleeding adult has no known congenital disorder and PT is relatively preserved.

  1. Repeat a correctly collected peripheral sample and review UFH, LMWH, DOAC exposure, thrombin time and anti-Xa evidence.
  2. Request immediate and incubated mixing, factor VIII, IX and XI assays and lupus anticoagulant-informed interpretation with the coagulation laboratory.
  3. If factor VIII is low, quantify the inhibitor and contact the haemophilia centre immediately rather than waiting for every aetiological test.

Key medicines

Recombinant activated factor VIIGive eptacog alfa 90 micrograms/kg by intravenous bolus every 2–3 hours until haemostasis is achieved, then lengthen the interval according to sustained clinical response under the haemophilia-centre protocol.Monitor clinically rather than with APTT. Arterial and venous thrombosis can occur, especially in older adults with vascular disease or cancer; avoid unplanned combination with activated PCC and record every dose and response.
Activated prothrombin-complex concentrateGive 50–100 units/kg intravenously every 8–12 hours according to bleeding response, with a maximum total dose of 200 units/kg in 24 hours.Do not exceed the daily ceiling. Monitor for DIC, myocardial, cerebral and venous thrombosis; use particular caution with emicizumab, sepsis, liver disease and recent sequential bypassing therapy.
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Sources and review status4 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.

  • BSH and UKHCDO: laboratory investigation and clinical management of acquired coagulation factor inhibitorsCurrent UK diagnosis, haemostatic treatment and inhibitor-eradication guidance.
  • NovoSeven 2 mg Summary of Product CharacteristicsLicensed recombinant activated factor VII dose, interval and thrombotic safety.
  • FEIBA Summary of Product CharacteristicsActivated prothrombin-complex dosing ceiling and safety information.
  • Obizur 500 U Summary of Product CharacteristicsRecombinant porcine factor VIII initial dosing and laboratory monitoring.

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 reviewJurisdictionUnited Kingdom