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.
Startle Disease, also known as inherited hyperekplexia, is a neurodegenerative disorder characterized by sudden and exaggerated startle responses to unexpected sensory stimuli, such as touch or sound. Affected dogs can show first signs in the weeks following their birth, which can include muscle hypertonicity (increased muscle tone), tremor-like activity, or episodes of collapse triggered by stimuli. It is possible for signs to improve when affected puppies are relaxed or sleeping. However, as signs progress, affected puppies can also demonstrate rear limb stiffness and may have difficulty ambulating by the time they are 3 to 5 months old.
Upon initial observation of clinical signs, affected dogs should be closely monitored to assess welfare. Due to the early onset and progressive nature of clinical signs, the prognosis is considered poor for affected dogs, and euthanasia is often considered based on welfare grounds.
This disorder is autosomal recessive, meaning two copies of the variant are needed for a dog to be at an elevated risk for being diagnosed with the condition. A carrier dog with one copy of the Startle Disease (Discovered in the Miniature American Shepherd) variant can be safely bred with a clear dog with no copies of the Startle Disease (Discovered in the Miniature American Shepherd) variant. About half of the puppies will have one copy (carriers) and half will have no copies of the variant. 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 disorder signs similar to the ones associated with this Startle Disease variant could develop due to a different genetic or clinical cause.