Hemophilia A/Factor VIII Deficiency (HEMA) in Boxers

Quick Summary

Hemophilia A/Factor VIII Deficiency is an inherited bleeding disorder in Boxers caused by a deficiency of the coagulation factor VIII (F8), a protein necessary for blood clotting.

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Phenotype: Affected dogs have variable presentation of the disease, with mild to moderate bleeding being observed. Additionally, affected dogs may bruise easily or have extended periods of bleeding following trauma. Frequent nosebleeds and stiffness may also indicate F8 deficiency. While bleeding is occasionally severe enough to result in death, most affected dogs have a normal lifespan.

Mode of Inheritance: X-linked recessive

Alleles: N = Normal/Unaffected, HEMAbx = Hemophilia A/Factor VIII Deficiency (Boxer variant)

Breeds appropriate for testing: Boxer

Explanation of Results:

  • Males only have one X chromosomes where females have two, therefore possible genotypes will differ by sex.
  • Female dogs with N/N genoytpe and male dogs with N genotype will not have Hemophilia A/Factor VIII Deficiency, and cannot transmit this variant to their offspring.
  • Female dogs with N/HEMAbx genotype will not have Hemophilia A/Factor VIII Deficiency, but are carriers. If a carrier female is bred to a normal male, all female puppies will be normal but 50% of them will be carriers. Among male puppies from this type of cross, 50% will be normal and 50% will be affected by Hemophilia A/Factor VIII Deficiency.
  • Female dogs with HEMAbx/HEMAbx genotype and male dogs with HEMAbx genotype will have Hemophilia A/Factor VIII Deficiency. A HEMAbx/HEMAbx genotype female dog will transmit this gene variant to all of her offspring, and a HEMAbx genotype male dog will transmit this gene variant to 50% of his offspring (all of his daughters).

Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)

Turnaround Time
At least 15 business days; may be delayed beyond 15 business days if sample requires additional testing, or a new sample is requested.
Price

$55 single test per animal ($5 discount on 3 or more dogs)

$25 as additional health test on same animal

Sample Collection

Dog DNA tests are carried out using cells brushed from your dog's cheeks and gums. The preferred cytology brushes are sent to you by mail, or you may provide your own brushes. For accepted alternative brushes, click here

We recommend waiting until puppies are at least three weeks old before testing.

 

Dog having its cheeks and gums brushed for DNA samples
Cheek and gum brushing technique for canine DNA sample collection

Step-By-Step:

  1. Make sure the dog has not had anything to eat or drink for at least 1 hour prior to collecting sample.
  2. When swabbing puppies, isolate each puppy from the mother, littermates and any shared toys for 1 hour prior to swabbing. Puppies should not have nursed or eaten for 1 hour prior to collecting sample.
  3. If collecting samples from more than one dog, make sure to sample one dog at a time and wash your hands before swabbing another dog.
  4. Label brush sleeve with name or ID of dog to be sampled.
  5. Open brush sleeve by arrow and remove one brush by its handle.
  6. Place bristle head between the dog’s gums and cheek and press lightly on the outside of the cheek while rubbing or rotating the brush back and forth for 15 seconds.
  7. Wave the brush in the air for 20 seconds to air dry.
  8. Insert brush back into sleeve.
  9. Repeat steps 5 - 8 for each unused brush in sleeve on a fresh area of cheek and gums. Make sure to use and return all brushes sent by the VGL. In most cases, it will be 3 brushes per dog. If using interdental gum brushes, please note that the VGL requires 4 brushes per dog and only moderate or wide interdental gum brushes are accepted.
  10. Do not seal brushes in sleeve.
  11. Place all samples in an envelope and return to the address provided.

ATTENTION:

  • Do not collect saliva/drool – the key to obtaining a good sample is getting cheek cells on the swab
  • Do not rub swab on the dog’s tongue or teeth – this will result in poor quality sample
  • Do not collect a sample from a puppy that has recently nursed – the mother’s genetic material can rub off on the puppy’s mouth and contaminate the sample
Additional Details

Hemophilia A is an inherited bleeding disorder caused by a deficiency of coagulation factor VIII (F8), an essential protein required for normal blood clotting. Affected dogs have variable presentation of the disease, with mild to moderate bleeding being observed. Additionally, affected dogs may bruise easily or have extended periods of bleeding following trauma. Frequent nosebleeds and stiffness may also indicate F8 deficiency resulting from excessive internal bleeding after damage to muscles and joints. While bleeding is occasionally severe enough to result in death, most affected dogs have a normal lifespan. Variable presentation coupled with a lack of observable incidents with bleeding often results in this condition going undetected until a dog has a surgical procedure or severe trauma.

In Boxers, F8 deficiency results from a c.1412C>G mutation in exon 10 (reported as HEMAbx). The disease is inherited in an X-linked recessive fashion. Females with two defective copies will show disease. Clinical signs are absent in females with one normal and one affected gene (carriers). Males have only one X chromosome. If the inherited allele is affected, males will show disease. If the inherited allele is normal, males do not have the disease.

Testing for this hemophilia A/Factor VIII deficiency variant can assist veterinarians with diagnosis of F8 deficiency and help breeders identify carriers among breeding females and affected breeding males to avoid mating pairs that can produce affected dogs. When a carrier female is bred to a normal male, all female puppies will be normal but 50% of them will be carriers. Among male puppies from this type of cross, 50% will be normal and 50% will be affected.

 

Note: This test does not detect the causative mutations for F8 deficiency in Old English Sheepdog, Irish Setter, or Miniature Schnauzer.
If you wish to test a German Shepherd Dog or German Shepherd-derived breed for Hemophilia A, click here for the breed-specific test.