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Progressive Retinal Atrophy (Discovered in the Miniature Long Haired Dachshund)

Progressive Retinal Atrophy (PRA) is an inherited disorder that results in degeneration of the light sensing retina at the back of the eye, leading to progressive vision loss and eventual blindness. Cone-rod dystrophy 1 (cord1-PRA) is one form that has a wide age range for clinical onset, from 6 months to 10 years old. The associated genetic risk variant has been identified in Dachshund breed types and the English Springer Spaniel.

Key Signs

Progressive vision loss, Blindness

Age of Onset

0 to 2 yrs

Juvenile onset

Inheritance

Autosomal Recessive

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.

Likelihood of the Condition

Low-moderate likelihood

At risk dogs may show signs of this disease in their lifetime, although many will not develop the condition due to absence of additional risk factors.

What to Do

Here’s how to care for a dog with cord1-PRA

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.

For Veterinarians

Here’s what a vet needs to know about cord1-PRA

Progressive Retinal Atrophy (PRA) comprises a group of inherited retinal dystrophies affecting dogs of various breeds. PRA is characterized by retinal degeneration and progressive loss of vision culminating in blindness. Unlike most PRAs, where rod photoreceptor cells degenerate first, in cone-rod dystrophy 1 (cord1-PRA) the cone cells usually begin to deteriorate first, followed by the rod cells. This means the photoreceptors which sense bright light and colors degenerate prior to the photoreceptors that sense dim light associated with night vision. The onset of clinical signs can range widely, from as early as 6 months old to as late as 10 years in age. It is proposed that genetic modifier variants can influence the timing in which an affected dog develops the onset of clinical signs. In one study, early ophthalmologic signs, such as changes to the granular appearance of the fundus, generalized tapetal hyperreflectivity, and retinal vascular attenuation, were detectable by 6 months of age in some affected dogs. In the reported cases, an electroretinogram (ERG) was greatly reduced in amplitude or largely extinguished by 10 months of age. However, there are other cases that do not show signs until late in life, if at all. Therefore, it is important to note that due to the wide age range for clinical onset and the fact that not all dogs with two copies of the risk variant will develop cord1-PRA, there is indication of modifier gene(s) involved in the expression of this variant which are not included in this panel test. Further research is needed to understand the penetrance of this variant, including its clinical relevance in dogs without Dachshund ancestry.

Although this condition results in gradual vision loss, and eventual blindness, many dogs adapt remarkably well to the loss of vision. And, while there is no treatment, owners should be advised that the dog may need assistance in unfamiliar surroundings as clinical signs progress. Owners may find that it is helpful to keep the dog's main environment as stable as possible (avoid moving furniture, etc.) to help them navigate as their vision declines. Precautions to protect the dog from threats they cannot visually detect (such as stairs, pools, etc.) should also be taken.

For Breeders

Planning to breed a dog with this genetic variant?

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 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 Progressive Retinal Atrophy (Discovered in the Miniature Long Haired Dachshund) variant can be safely bred with a clear dog with no copies of the Progressive Retinal Atrophy (Discovered in the Miniature Long Haired Dachshund) variant. About half of the puppies will have one copy (carriers) and half will have no copies of the variant. Furthermore, a dog with two copies of this Progressive Retinal Atrophy variant can be safely bred with a clear dog. The resulting puppies will all be carriers. 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 Progressive Retinal Atrophy variant could develop due to a different genetic or clinical cause.

Technical Details

Gene RPGRIP1
Variant Insertion
Chromosome 15
Coordinate Start 18,332,036
Coordinate End 18,332,037

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Mellersh, C. S., Boursnell, M. E. G., Pettitt, L., Ryder, E. J., Holmes, N. G., Grafham, D., … Vaudin, M. (2006). Canine RPGRIP1 mutation establishes cone-rod dystrophy in miniature longhaired dachshunds as a homologue of human Leber congenital amaurosis. Genomics, 88(3), 293–301. View the article