Breeds Affected: Cavalier King Charles Spaniel
Samples Accepted: Blood, Buccal Swabs
Disease Information: Asymptomatic macrothrombocytopenia (AM) is a disorder of platelet formation.
Inheritance Information: Asymptomatic Macrothrombocytopenia 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 affected offspring.
N/am The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/am carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
am/am The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/am carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/am 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/am x N/am) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (am/am) should not be used for breeding.
Test Information: This mutation test identifies a single base pair change in the TUBB1 gene.
Davis, B., Toivio-Kinnucan, M., Schuller, S., Boudreaux, MK.: Mutation in beta1-tubulin correlates with macrothrombocytopenia in Cavalier King Charles Spaniels. J Vet Intern Med 22:540-5, 2008. Pubmed reference: 18466252. DOI: 10.1111/j.1939-1676.2008.0085.x.
Further information is available at the Online Mendelian Inheritance in Animals website.