Haemophilia B (Factor IX Deficiency)
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
Emergency presentation is possiblePlasma products provide factor IX and are the mainstay of emergency treatment.
Breeding advice appliesUse the condition’s screening guidance and veterinary or genetics advice before breeding an affected or at-risk animal.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Haemophilia B is an inherited bleeding disorder caused by reduced activity of clotting factor IX. Factor IX is one of the proteins required to build and stabilise a durable blood clot after a blood vessel is damaged. When too little functional factor IX is present, bleeding continues longer than normal even though platelet numbers and the initial platelet response may be adequate.
The disorder is usually X-linked recessive. Males have only one X chromosome, so a male that inherits a disease-causing variant will be affected. Females are more commonly clinically normal carriers, although the genetics of individual families can be more complex. Haemophilia B has been reported in a number of dog breeds, and different mutations can occur in different populations.
Clinical severity reflects the amount of factor IX activity that remains. Dogs with mild deficiency may appear completely normal until surgery, dental work or trauma causes unexpectedly prolonged bleeding. More severely affected dogs can develop spontaneous bruising, bleeding into muscles or joints, swelling and lameness, nose or mouth bleeding, or internal haemorrhage. Puppies with extremely low factor activity may die early from uncontrolled bleeding.
A routine coagulation profile typically shows a prolonged activated partial thromboplastin time with a normal prothrombin time. This pattern suggests a defect in the intrinsic clotting pathway but does not by itself distinguish haemophilia A from haemophilia B. A specific factor IX activity assay is required for confirmation.
Because affected dogs can look healthy between bleeding episodes, diagnosis before an elective procedure is particularly valuable.
Haemophilia B is particularly concerning in a male dog from a family with unexplained bleeding, because carrier females may have no outward signs. Very low activity is associated with a greater risk of spontaneous, life-threatening bleeding.
Screening & Early Detection
A prolonged activated partial thromboplastin time combined with a normal prothrombin time is compatible with factor VIII or factor IX deficiency and should prompt more specific testing.
Factor IX activity measurement is used to confirm haemophilia B and can help estimate severity. The test is usually performed by a specialist laboratory, and correct sample handling is important for an accurate result.
Where a breed-specific DNA test is available for the family’s mutation, genetic screening can identify affected males and carrier females before breeding. A negative DNA result only excludes the mutation included in that particular test; it does not rule out every possible factor IX variant across all breeds.
Seek investigation for unexplained bruising, prolonged bleeding from small wounds, swollen painful joints or muscles, or excessive bleeding after tooth loss, desexing or surgery. Male dogs from affected lines should ideally be assessed before elective procedures. When an affected dog is identified, female relatives may be carriers and should be considered for genetic counselling or testing where an appropriate assay exists.
DNA tests are available for some breed-specific mutations. Severe haemorrhage after a seemingly minor operation may be the first sign in an undiagnosed dog, making family history and appropriate pre-operative testing important.
Treatment & Management
Haemophilia B cannot usually be cured, so treatment focuses on replacing clotting factor during bleeding episodes and preventing avoidable haemorrhage. Plasma products provide factor IX and are the mainstay of emergency treatment. Dogs that have lost a substantial volume of blood may also require whole blood or packed red cells to correct anaemia and support circulation.
Internal bleeding, rapidly enlarging bruises, severe weakness, neurological signs or suspected haemorrhage into the chest or abdomen requires urgent hospital care. Bleeding into joints can be painful and, when repeated, may cause chronic joint damage. Activity is restricted during active haemorrhage while clotting support is provided.
Elective procedures should be planned rather than approached as routine. The veterinary team should know the dog’s diagnosis in advance, arrange access to appropriate blood products and use meticulous haemostatic techniques. Medications that increase bleeding tendency, including some anti-inflammatory drugs, should only be used with veterinary guidance.
At home, the aim is sensible risk reduction rather than complete inactivity. Rough impact sports and situations likely to cause major trauma are avoided, while normal low-risk activity can usually continue. Know what unexplained swelling or pallor may mean and seek help early.
Management also means planning ahead for dental work, desexing or any other invasive procedure. The veterinary team may arrange appropriate blood products before intervention, while sudden swelling, weakness, pale gums, lameness or unexplained pain should trigger assessment for concealed bleeding.
Breeds or species affected
Airedale Terrier
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Alaskan malamute
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American Cocker Spaniel
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Bichon frise
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Black and tan coonhound
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Bull terrier
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Cairn terrier
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French bulldog
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German shepherd
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German Wirehaired Pointer
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Labrador retriever
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Lhasa apso
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Old English sheepdog
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Rhodesian ridgeback
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St Bernard
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Scottish terrier
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Shetland sheepdog
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