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.

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)

Price

$50 one test per animal
$30 as additional test (same animal)
$45 for 3 or more dogs

Panels Available
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.
Turnaround Time
5-10 business days

Species

Dog

Breed

Type of Test

Results Reported As
Test Result Hemophilia A/Factor VIII Deficiency
N/N Normal female. No copies of F8 mutations.
N/HEMAbx Carrier female. 1 copy of the HEMAbx mutation.
HEMAbx/HEMAbx Affected female. 2 copies of the HEMAbx mutation.
N Normal male. No copies of the F8 mutations.
HEMAbx Affected male. 1 copy of the HEMAbx mutation.
References

Mischke, R., Wilhelm, C., Czwalinna, A., Varvenne, M., Narten, K., & Depka, M. V. (2011). Canine haemophilia A caused by a mutation leading to a stop codon. Veterinary Record, 169(19), 496-496. doi: 10.1136/vr.d4677

Christopherson, P. W., Bacek, L. M., King, K. B., & Boudreaux, M. K. (2014). Two novel missense mutations associated with hemophilia A in a family of Boxers, and a German Shepherd dog. Veterinary Clinical Pathology, 43(3), 312-316. doi: 10.1111/vcp.12172