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Hemophilia B (Discovered in the Lhasa Apso)

Hemophilia B, also known as Factor IX Deficiency, is a blood clotting disorder most commonly seen in male dogs, which can result in prolonged bleeding after an injury or a surgical procedure.

Key Signs

Excessive or life threatening bleeding

Age of Onset

At birth

Present at birth


X-linked Recessive

For X-linked recessive disorders, the genetic variant is found on the X chromosome. Female dogs must have two copies of the variant to be at risk of developing the condition, whereas male dogs only need one copy to be at risk. Males and females with any copies of the variant may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with Hemophilia B

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about Hemophilia B

Blood coagulation is a complex process. Factor IX is one of the proteins necessary for blood coagulation and its deficiency causes hemophilia B in an affected dog. Hemophilia B is a milder blood disorder than hemophilia A, but it may still cause life-threatening bleeding. Specific factor assay may be measured by a reference laboratory. Prior to surgery or invasive procedures, a prothrombin (PT) and partial thromboplastin time (PTT) should be measured. Additional supportive measures, including transfusions, may be necessary. Excessive and prolonged bleeding may be observed during tooth extractions, routine surgeries, and even minor traumas. The condition is usually more severe for active dogs of large size.

Prior to surgery or invasive procedures, a prothrombin (PT) and partial thromboplastin time (PTT) should be measured. Affected dogs should be monitored closely for excessive and prolonged bleeding during and after any required surgical procedures or after any trauma. Blood or platelet transfusions should be provided as necessary to ensure proper clotting if other means are unsuccessful. If multiple transfusions are needed, then it is good to measure the inhibition of factor IX activity which, if present, may require increased transfusion therapy or potentially concurrent corticosteroid treatment.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disorder is X-linked recessive, meaning the genetic variant is found on the X chromosome. Given males only have one X chromosome, a single affected copy will increase the risk of being diagnosed with the disorder. Females typically require two copies to be at an elevated risk. Use of dogs with one or two copies of the variant is not recommended for breeding as there is a risk that the resulting litter will contain affected puppies. Please note: It is possible that clinical signs similar to the ones caused by this variant could develop due to a different genetic or clinical cause.

Technical Details

Gene FIX
Variant Deletion
Chromosome X
Coordinate Start 109,521,356
Coordinate End 109,521,361

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Brooks, M. B., Gu, W., Barnas, J. L., Ray, J., & Ray, K. (2003). A Line 1 insertion in the Factor IX gene segregates with mild hemophilia B in dogs. Mammalian Genome, 14(11), 788–795. View the article

Gu, W., Brooks, M., Catalfamo, J., Ray, J., & Ray, K. (1999). Two distinct mutations cause severe hemophilia B in two unrelated canine pedigrees. Thrombosis and Haemostasis, 82(4), 1270–1275. View the article

Evans, J. P., Brinkhous, K. M., Brayer, G. D., Reisner, H. M., & High, K. A. (1989). Canine hemophilia B resulting from a point mutation with unusual consequences. Proceedings of the National Academy of Sciences of the United States of America, 86(24), 10095–10099. View the article

Mauser, A. E., Whitlark, J., Whitney, K. M., & Lothrop, C. D. (1996). A deletion mutation causes hemophilia B in Lhasa Apso dogs. Blood, 88(9), 3451–3455. View the article

Mischke, R., Kühnlein, P., Kehl, A., Langbein-Detsch, I., Steudle, F., Schmid, A., … Müller, E. (2011). G244E in the canine factor IX gene leads to severe haemophilia B in Rhodesian Ridgebacks. Veterinary Journal, 187(1), 113–118. View the article