Haemophilia A (Factor VIII 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.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Haemophilia A is an inherited bleeding disorder caused by inadequate activity of clotting factor VIII. Factor VIII is part of the coagulation cascade that stabilises a blood clot after a vessel is damaged. When its activity is severely reduced, the initial platelet plug cannot be reinforced normally and bleeding continues for much longer than expected.
The disorder is usually X-linked recessive. Males have only one X chromosome, so a male that inherits the disease-causing variant is affected. Females are more often clinically normal carriers because their second X chromosome can provide functional factor VIII. The condition has been reported in many breeds and crossbreeds, with German Shepherd Dogs among the better-known affected populations. Different families can carry different mutations.
Severity depends largely on how much factor VIII activity remains. Mildly affected dogs may only bleed excessively after surgery or significant trauma. More severe cases can develop large bruises, prolonged bleeding from wounds, haemorrhage into muscles or joints, or internal bleeding into body cavities. Puppies with extremely low activity can die from spontaneous or neonatal haemorrhage.
Routine platelet numbers are usually normal because the problem is in secondary coagulation rather than platelet production. An activated partial thromboplastin time is typically prolonged while prothrombin time remains normal, which provides an important clue.
Haemophilia A cannot be recognised reliably by appearance because an affected dog may seem completely healthy until an injury or procedure exposes the clotting defect. Knowing the diagnosis before desexing, dental work or surgery is therefore particularly important, allowing blood products and a haemostasis plan to be available in advance.
The practical risk is often hidden until normal clotting is challenged. A dog may appear healthy in everyday life yet develop serious haemorrhage after trauma, tooth loss or surgery, making advance recognition especially important before any procedure expected to cause bleeding.
Sample collection and handling are important because clotting proteins can deteriorate if processing is delayed.
Screening & Early Detection
A coagulation profile is a useful first screening step when haemophilia is suspected or when a male dog from an affected family is being assessed before surgery. In classic haemophilia A, the activated partial thromboplastin time is prolonged while the prothrombin time remains within the reference range. This pattern is not unique to factor VIII deficiency, so it should be followed by a specific factor assay.
Factor VIII activity testing confirms the functional deficiency and helps indicate severity. Testing is commonly performed through a specialist laboratory. Some families or breeds have DNA tests for a known mutation, but no single genetic test detects every possible cause of canine haemophilia A.
Report unexplained large bruises, prolonged bleeding after minor wounds, swelling of a joint without obvious injury, or continued bleeding after tooth loss or surgery. Affected male puppies can appear normal between episodes.
When an affected male is identified, his mother and female relatives may be carriers and deserve genetic counselling or testing where a family-specific mutation is available. Screening before an elective procedure is especially valuable because discovering severe haemophilia only after uncontrolled surgical bleeding creates a preventable emergency.
Definitive diagnosis uses a factor VIII activity assay at a specialist laboratory.
Treatment & Management
Haemophilia A is managed rather than routinely cured, with treatment aimed at replacing missing clotting activity during significant bleeding and preventing avoidable trauma. Fresh frozen plasma or other plasma products provide factor VIII and can control many haemorrhages. Whole-blood or red-cell transfusion may also be required when substantial blood loss has caused anaemia.
The amount and frequency of transfusion depend on the site and severity of bleeding. Internal haemorrhage, significant muscle swelling, neurological signs or suspected bleeding into the chest or abdomen requires urgent hospital care. Painful swollen joints should be treated carefully because repeated haemarthrosis can cause chronic joint damage.
Elective surgery should be planned in advance with a veterinarian who knows the dog’s diagnosis. Blood products need to be available, and the procedure should use meticulous haemostatic technique. Drugs that impair platelet function, including some anti-inflammatory medications, may increase bleeding risk and should only be used when the treating veterinarian considers them safe.
At home, management focuses on reducing high-risk trauma without unnecessarily restricting normal life. Avoid rough activities likely to cause major impact and should seek veterinary advice before dental procedures or invasive tests.
Every procedure should be planned with the clotting disorder in mind. The veterinary team may arrange factor-containing blood products in advance and minimise injections or tissue trauma. At home, sudden swelling, unexplained pain, weakness, pale gums or prolonged bleeding warrants prompt assessment for internal haemorrhage.
Breeds or species affected
Beagle
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Bichon frise
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Black and tan coonhound
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Cairn terrier
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Chihuahua
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Collie
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Collie (rough & smooth)
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English setter
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French bulldog
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German shepherd
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German shorthaired pointer
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Golden retriever
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Greyhound
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Hungarian Vizsla
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Irish setter
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Labrador retriever
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Old English sheepdog
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Samoyed
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Scottish terrier
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Shetland sheepdog
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Siberian husky
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Weimaraner
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