Congenital Macrothrombocytopenia

Test Overview:

Canine Macrothrombocytopenia is a condition characterized by oversized platelets and a low platelet count. The name is derived from words macro (large) and thrombocyte (platelets). Canine Macrothrombocytopenia is characterized by abnormalities in size and count of platelets. Platelets in affected dogs function normally, and affected dogs do not show any health problems or prolonged bleeding time. Dogs affected with this mutation usually have platelet numbers ranging between 20,000 and 90,000/µl while carriers usually have intermediate platelet numbers ranging from 100,000 to 250,000/µl Having said all that, Dr. Penny Watson of the University of Cambridge, who has been studying pancreatitis in cavaliers for many years, opened at a presentation in November 2014 the hypothesis that there may be a relationship between the serotonin carried by blood platelets through the vascular system to various organs, particularly the pancreas, the kidneys, the liver, the central nervous system, and the mitral valves of the heart, all causing scarring of and other damage to the tissues of these organs. It may prove useful in understanding heart-related changes in macrothrombocytopenic CKCS with concurrent mitral valve regurgitation.


Haemolymphatic - Associated with the blood and lymph


Tubulin beta 1 class VI (TUBB1) on Chromosome 24

Variant Detected:

Base Substitution c.745G>A p.Asp249Asn


Low-Moderate. This disease can cause some discomfort and/or dysfunction in the affected animal. It does not generally affect life expectancy.

Mode of Inheritance:

Autosomal Recessive

Research Citation(s):

Davis B, et al. Mutation in beta1-tubulin correlates with macrothrombocytopenia in Cavalier King Charles Spaniels. (2008) J Vet Intern Med 22(3); 540-545.

Associated Breed(s):

Australian Cobberdog, Australian Labradoodle , Bernardoodle, Cavador, Cavalier King Charles Spaniel, Cavoodle, Chihuahua, Goldendoodle, Labradoodle , Labradoodle Retrodoodle , Labrador Retriever, Miniature Poodle, Mixed Breed, Parson Russell Terrier, Standard Poodle, Toy Poodle,