Faktor IX Deficiency | Haemophilia B (F9 Rhodesian Ridgeback)
Factor IX deficiency or haemophilia B (F9 deficiency) is a blood coagulation disorder. Factor 9 is a glycoprotein and plays an important role in the signalling cascade of blood clotting. When the disease occurs, there is a deficiency of factor 9, which causes the affected animals to show symptoms such as intense and prolonged bleeding when injured (e.g. also after surgery).
This genetic variant of the disease occurs in the Rhodesian Ridgeback. The disease is inherited in an X-linked recessive manner.
Synonym: Christmas disease
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Symptoms
- Intense and persistent bleeding from injuries (e.g. also after operations).
- Poor wound healing
- Frequent nosebleeds
- Haematomas
- Bleeding disorders in pregnant bitches or in those that have already given birth
General Information
- Factor IX deficiency or haemophilia B (F9 deficiency) is a blood coagulation disorder.
- Factor 9 is an enzyme (protein with a special catalytic function) and plays an important role in the signalling cascade of blood clotting.
- If factor 9 is deficient, the signalling cascade for blood clotting is reduced or not triggered at all.
Breeds affected
Rhodesian Ridgeback
Test Information
This test detects a missense mutation (c.731G>A) in exon 7 of the F9 gene, which causes haemophilia B in Rhodesian Ridgebacks.
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This test is carried out by a partner laboratory.
Other mutations causing haemophilia B have been found in other breeds. For those this test does not test.
- Airedale Terrier: Insertion in exon 8 of the F9 gene.
- Cairn Terrier: Missense mutation (c.1477G>A) in the F9 gene
- Hovawart: Mutation in the regulatory unit of the F9 gene
- Labrador Retriever: Deletion of the F9 gene
- Lhasa Apso: Deletion in the F9 gene
Genotype and Lab Report
Inheritance: X-linked recessive.
The affected gene is located on the X chromosome. Male dogs with this mutation are affected (X-f9/Y). Females are affected if both X chromosomes are affected (X-f9/X-f9). They can also have one normal chromosome and one mutated chromosome and thus be asymptomatic carriers (X/X-f9).
Genotypes:
X/X
The dog is a healthy female.
X/X-f9
The dog is a carrier female. It is healthy but can pass on 50% of the mutation (X-f9) to the offspring.
X-f9/X-f9
The dog is an affected female and usually does not reach breeding maturity.
X/Y
The dog is a healthy male.
X-f9/Y
The dog is an affected male and usually does not live long enough to reproduce. If this is the case, 50% of the mutation is passed on to the offspring (females). All female offspring are carriers.
Recommendations
- Carrier females (X/X-f9) should not be used for breeding.
- Female offspring of a carrier female should be tested for their genotype (X/X or X/X-f9 possible).
- Affected animals should be excluded from breeding if they reach breeding age.
Literature
Mischke, R., Kühnlein, P., Kehl, A., Langbein-Detsch, I., Steudle, F., Schmid, A., Dandekar, T., Czwalinna, A., Müller, E.: G244E in the canine factor IX gene leads to severe haemophilia B in Rhodesian Ridgebacks. Vet J 187:113-8, 2011. Pubmed reference: 20303304. DOI: 10.1016/j.tvjl.2010.01.017.
Further information is available at: Online Mendelian Inheritance in Animals.