Macrothrombocytopenia (MTC-R) DNA Testing for Norfolk Terriers

The Norfolk terrier is one of the UK's remaining native dog breeds, known for being lively, intelligent, and affectionate companions. While generally robust, this breed can carry certain hereditary health conditions, including macrothrombocytopenia (MTC-R), a genetic blood disorder.

Understanding MTC-R helps owners and breeders make informed decisions to promote the health and well-being of Norfolk terriers through DNA testing and responsible breeding.

What is Macrothrombocytopenia (MTC-R)?

Macrothrombocytopenia (MTC-R) is a hereditary disorder characterised by a low blood platelet count (thrombocytopenia) and abnormally large platelets (macrothrombocytes). This condition is congenital, meaning affected dogs are born with it due to specific genetic mutations in the ß1-tubulin gene (TUBB1).

Although it affects platelet size and number, most Norfolk terriers with MTC-R show no clinical signs such as spontaneous bleeding or clotting problems. Often, the condition is discovered incidentally during routine blood tests. Since MTC-R does not respond to typical treatments for acquired low platelet counts, accurate diagnosis is crucial to avoid unnecessary or harmful therapies.

How is MTC-R Inherited in Norfolk Terriers?

The MTC-R disorder is inherited in an autosomal recessive manner. This means:

• Dogs with two copies of the mutated gene (homozygous) are affected and have low platelet counts with large platelets.
• Dogs with only one copy of the mutation (carriers) do not show symptoms and have normal platelet counts.
• If neither parent carries the mutation, the litter will be clear.

Breeding decisions depend on understanding the genetic status of both parents. The genetic inheritance pattern results in different probabilities for offspring as follows:

• Two clear parents: All puppies are clear of the mutation.
• Two affected parents: All puppies are affected.
• Two carrier parents: 25% affected, 50% carriers, 25% clear.
• One clear and one carrier parent: 50% carriers, 50% clear.
• One clear and one affected parent: All puppies are carriers.
• One carrier and one affected parent: 50% affected, 50% carriers.

Why DNA Testing for MTC-R is Important

DNA testing is the most reliable way to identify whether a Norfolk terrier is clear, a carrier, or affected by MTC-R. It plays a crucial role in:

• Confirming diagnosis to avoid misdiagnosing the condition as an acquired blood disorder.
• Preventing unnecessary treatments such as corticosteroids or antibiotics.
• Helping breeders make responsible mating decisions to prevent affected puppies.
• Informing owners about their dog's health status and guiding veterinary care.

How to Get Your Norfolk Terrier DNA Tested for MTC-R

If you are a breeder or owner wishing to know your Norfolk terrier's genetic status, consult your vet. Your vet can collect a cheek swab or blood sample and send it to an approved genetic testing laboratory in the UK for analysis.

For responsible breeding, it is essential that both prospective parent dogs are tested before mating. This ensures knowledge of each dog's status and allows informed decisions to avoid producing affected litters.

Advice for Norfolk Terrier Owners and Breeders in the UK

• Test all breeding dogs: To uphold breed health, DNA test all Norfolk terriers considered for breeding.
• Avoid carrier to carrier matings: This reduces the risk of affected puppies and maintains breed vitality.
• Educate new owners: Explain that MTC-R is usually benign and does not typically affect quality of life.
• Consult your vet: If your dog has low platelets, a genetic test can clarify the diagnosis to avoid unnecessary treatments.
• Maintain regular health checks: Routine vet visits help ensure general wellness; MTC-R itself rarely requires treatment.
• Support breed health registries: Reporting MTC-R status helps monitor the condition's prevalence and supports ethical breeding.

Summary

Macrothrombocytopenia (MTC-R) in Norfolk terriers is a hereditary, benign blood disorder causing low platelet counts and large platelets. DNA testing is vital for accurate diagnosis and responsible breeding to prevent affected litters. Most affected dogs lead normal lives without special treatment. Working closely with your vet and using genetic testing supports healthy breeding and helps protect the welfare of this cherished UK native breed.