Breeds Affected: Great Pyrenees
Samples Accepted: Blood, Buccal Swab
Disease Information: Glanzmann Thrombasthenia (GT) is a bleeding disorder caused by defective platelets. Type I GT is characterized by having less than five percent of the normal number of platelets.
Inheritance Information: Glanzmann Thrombasthenia is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers.
The possible genotypes are:
N/N The dog is normal, and cannot produce GT-affected offspring.
N/gt The dog is a carrier of GT, and can pass the allele on to approximately 50% of any offspring. If bred to another N/gt carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
gt/gt The dog is affected with GT. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/gt carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/gt x N/N) without any risk of producing affected offspring. The offspring should be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/gt x N/gt) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (gt/gt) should not be used for breeding.
Test Information: This mutation test identifies a 14 base pair insertion in exon 13 of the ITGA2B gene. Animals which have two copies of this allele are affected with GT, and animals with one copy are clinically-normal carriers.
Lipscomb, D.L., Bourne, C., Boudreaux, M.K. : Two genetic defects in alpha(IIb) are associated with type I Glanzmann’s thrombasthenia in a Great Pyrenees dog: A 14-base insertion in exon 13 and a splicing defect of intron 13 Veterinary Pathology 37:581-588, 2000. Pubmed reference: 11105947.
Further information is available at the Online Mendelian Inheritance in Animals website.