UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory

Hemophilia A/Factor VIII Deficiency

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.


Two independent mutations in the Factor VIII gene result in German Shepherd Dog F8 deficiency: c.98G>A (reported as HEMA-1) and c.1643G>A (reported as HEMA-2). 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.


The Veterinary Genetics Laboratory offers genetic tests for Hemophilia A. Test results 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.

Testing recommended for:  German Shepherd Dog, Shiloh Shepherd, White Shepherd Dog, Boxer, (This test does not detect the causative mutations for F8 deficiency in Old English Sheepdog, Irish Setter or Miniature Schnauzer)

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Allow 5-10 business days for results.

Results reported as:

N/N

Normal female - no copies of F8 mutations.

N/HEMA*

Carrier female - 1 copy of the HEMA* mutation

HEMA/HEMA*

Affected female - 2 copies of the HEMA* mutation

N

Normal male - no copies of the F8 mutations

HEMA*

Affected male - 1 copy of the HEMA* mutation

 

 

 

* Report will specify HEMA-1, HEMA-2 or HEMAbx according to breed and mutation present.

References:

Christopherson PW, Bacek LM, King KB, Boudreaux MK. (2014) Two novel missense mutations associated with hemophilia A in a family of Boxers, and a German Shepherd dog. Vet Clin Pathol 43:312-316.


Mischke R, Wilhelm Ch, Czwalinna A, Varvenne M, Narten K, von Depka M. (2011) Canine haemophilia A caused by a mutation leading to a stop codon. Vet Rec 169:496b.

Veterinary Genetics Laboratory Tel 530-752-2211 Email VGL