For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.
At risk dogs are highly likely to show signs of this disease in their lifetime.
Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.
Clinical signs of this condition are usually first detected when the puppy is between 2 to 6 months of age. The first observable sign of spinocerebellar ataxia is lack of muscle coordination, particularly evident in the pelvic limbs. They may also exhibit hypermetria, myokymia (muscle fasciculations), neuromyotonia (muscle twitching at rest), excessive facial rubbing, and seizures. Affected dogs are often euthanized due to difficulties walking.
Depending on the severity of the clinical signs, a dog can be supported to reduce the likelihood of injury when moving around. Stairs may pose a particular risk and should be avoided. Medical control of seizures can be attempted. However, humane euthanasia may be elected.
There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.
This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the SAMS mutation can be safely bred with a clear dog with no copies of the SAMS mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the SAMS mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the SAMS mutation could develop due to a different genetic or clinical cause.
All coordinates reference CanFam3.1
Gilliam, D., O’Brien, D. P., Coates, J. R., Johnson, G. S., Johnson, G. C., Mhlanga-Mutangadura, T., … Schnabel, R. D. (2014). A homozygous KCNJ10 mutation in jack russell terriers and related breeds with spinocerebellar ataxia with myokymia, seizures, or both. Journal of Veterinary Internal Medicine, 28(3), 871–877. View the article
Rohdin, C., Gilliam, D., O’Leary, C. A., O’Brien, D. P., Coates, J. R., Johnson, G. S., & Jäderlund, K. H. (2015). A KCNJ10 mutation previously identified in the Russell group of terriers also occurs in Smooth-Haired Fox Terriers with hereditary ataxia and in related breeds. Acta Veterinaria Scandinavica, 57(1), 1–4. View the article