Startle disease or hyperekplexia is an inherited neurologic disorder affecting Irish Wolfhounds. Affected pups typically present between 5-7 days of age with rigid limbs and tremors when handled. Symptoms stop when puppies are relaxed or sleeping. Affected pups are unable to stand and are smaller than normal littermates. They may stop breathing and turn blue while suckling. Due to poor quality of life, affected pups are often euthanized within the first few months of life.
Genetic testing of the SLC6A5 gene will reliably determine whether a dog is a genetic Carrier of startle disease. Startle disease is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the SLC6A5 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Gill JL, Capper D, Vanbellinghen JF, Chung SK, Higgins RJ, Rees MI, Shelton GD, Harvey RJ. Startle disease in Irish wolfhounds associated with a microdeletion in the glycine transporter GlyT2 gene. Neurobiol Dis. 2011 Jul; 43(1):184-9.