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Horse Thrombasthenia - Quarter Horse and Thoroughbred
| Acronym: | TBA1 |
| Gene: | ITGA2B |
| Mutation: | c.122G>C |
| Inheritance: | Autosomal Recessive |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Thrombasthenia is an inherited blood disease that affects several breeds of horses. Horses with thrombasthenia have epistaxis (nosebleeds) and persistent and spontaneous bleeding starting from birth. Thrombasthenia is caused by a genetic mutation in the integrin alpha 2b (ITGA2B) gene responsible for binding fibrinogen and allowing aggregation of activated platelets to form a clot at the injury site. Two mutations in the ITGA2B gene cause this disease - one is a missense mutation leading to integrin deficiency, and the other is a deletion affecting integrin function, so it doesn’t bind to fibrinogen. Both mutations inhibit clot formation, generating the same clinical signs of the disease.
Thrombasthenia is inherited as an autosomal recessive trait, meaning that two copies of the mutation are needed for a horse to be affected. Thrombasthenia affects a couple of horse breeds, including Oldenburger, Quarter Horse, Thoroughbred, and Peruvian Horse. The disease is incurable, but early detection by genetic testing can help in managing the symptoms of the disease, as well as with the prevention of further breeding of affected horses.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Dahlgren, A. R., Tablin, F., & Finno, C. J. (2020). Genetics of equine bleeding disorders. Equine Veterinary Journal. doi:10.1111/evj.13290
Sanz, M. G., Wills, T. B., Christopherson, P., & Hines, M. T. (2011). Glanzmann thrombasthenia in a 17-year-old Peruvian Paso mare. Veterinary Clinical Pathology, 40(1), 48–51. doi:10.1111/j.1939-165x.2011.00289.x