Affected gene: TUBB1
Inheritance: Autosomal recessive
Mutation: CanFam3.1 24 g.43766144G>A c.745G>A
OMIA link:002434-9615

Breeds: Cavalier King Charles Spaniel

Symptoms:
Macrothrombocytopenia (also called thrombocytopenia) is caused by a mutation in the β1-tubulin gene and causes a decrease in the number of platelets in the blood. Hemostatic function is not impaired, probably because of the presence of a normal circulating platelet mass. The prevalence of asymptomatic macrothrombocytopenia in the CKCS is very high, with more than 90% of dogs being either carriers or affected. Several other breeds and mixed breed dogs have also been identified with this mutation.

References:
Gelain ME, Bertazzolo W, Tutino G et al. (2014) A novel point mutation in the beta1-tubulin gene in asymptomatic macrothrombocytopenic Norfolk and Cairn Terriers.  Vet Clin Pathol. 43(3):317-21. [pubmed/25060661]
Gelain ME, Tutino GF, Pogliani E, Bertazzolo W. (2010) Macrothrombocytopenia in a group of related Norfolk terriers. Vet Rec 167:493-4. [pubmed/20871084]
Davis B, Toivio-Dinnucan M, Schuller S, Boudreaux MK. (2008) Mutation in Beta1-tubulin correlates with macrothrombocytopenia in Cavalier King Charles Spaniels.  J Vet Int Med 22:540-545. [pubmed/18466252]