Haemophilia type B

Haemophilia B is caused by a deficiency of coagulation factor IX and manifests itself as a bleeding disorder. Affected individuals are more prone to bleeding during routine veterinary procedures (e.g. vaccinations), may bleed from the gums and form haematomas to a greater extent. Complications arise in the case of major bleeding injuries or during surgery when it is difficult to stop the bleeding.

The disease is caused by the nonsense mutation c.1150C>T in the F9 gene, which encodes coagulation factor IX.

The mutation is X-linked. This means that it is localized on the X chromosome. Since the genotype of males is composed of X and Y chromosomes, only healthy (unaffected by the mutation) males can be unaffected. The female genotype contains two X chromosomes, so females can be either healthy, carriers or affected (very rare in practice). Female carriers do not show clinical signs but are able to pass the mutant allele to their offspring. The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected kittens.

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References:

Goree, M., Catalfamo, J.L., Aber, S., Boudreaux, M.K. : Characterization of the mutations causing hemophilia B in 2 domestic cats. J Vet Intern Med 19:200-4, 2005. Pubmed reference: 15822564.