Hemophilia B (Cairn Terrier Type)

Other Names: Christmas disease, Factor IX deficiency
Affected Genes: F9
Inheritance: X-Linked Recessive
Mutation: chrX:109532018 (canFam3): G>A
Breed(s): Cairn Terrier

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Common Symptoms

Hemophilia B (Cairn terrier type) is an inherited bleeding disorder affecting dogs. Hemophilia B (Cairn terrier type) is caused by a deficiency of coagulation factor IX, an essential protein needed for normal blood clotting. There is variation between breeds in the severity of the bleeding tendency with this disease. More severely affected dogs bruise easily and often get blood filled masses (hematomas) under their skin and within muscles with mild trauma. They can also have internal bleeding and bloody or dark tarry feces. Dogs may show signs of lameness or stiffness if bleeding in the joints is present. A mildly affected dog may present with easy and excessive bruising and frequent nosebleeds. There is significant risk for prolonged bleeding after surgery or trauma, and in some cases, the bleeding may be severe enough to cause death. Veterinarians performing surgery on known affected dogs should have ready access to blood banked for transfusions. Most dogs will have a normal lifespan with this condition despite increased blood clotting times.

Testing Tips

Genetic testing of the F9 gene will reliably determine whether a dog is a genetic Carrier of hemophilia B (Cairn terrier type). Hemophilia B (Cairn terrier type) is inherited in an X-Linked Recessive manner in dogs meaning that female dogs must receive two copies of the mutated gene (one from each parent) to develop the disease while male dogs only require one copy of the mutated gene from the mother in order to develop disease. Therefore, male dogs more commonly present with symptoms of the disease. Each male pup that is born to a female dog known to be a carrier of hemophilia B has a 50% chance of inheriting the disease. Female dogs that are not carriers of this Mutation have no increased risk of having affected pups. Reliable genetic testing is important for determining breeding practices. Because female carriers generally do not have features of the disease, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.


  • Brinkhous KM, Davis PD, Graham JB, Dodds WJ. Expression and linkage of genes for X-linked hemophilias A and B in the dog. Blood. 1973 Apr;41(4):577-85. [PubMed: 4688873]
  • Evans JP, Brinkhous KM, Brayer GD, Reisner HM, High KA. Canine hemophilia B resulting from a point mutation with unusual consequences. Proc Natl Acad Sci U S A. 1989 Dec; 86(24):10095-9. [PubMed: 2481310]
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