Progressive retinal Atrophy, Rod-cone dysplasia 3 is an inherited eye disease affecting dogs. Progressive retinal atrophy, Rod-cone dysplasia 3 occurs as a result of degeneration of both rod and cone type Photoreceptor Cells of the Retina, which are important for vision in dim and bright light, respectively. Affected dogs have abnormal thinning and degeneration of the retina beginning around 4 weeks of age. Signs of progressive retinal atrophy including changes in reflectivity and appearance of a structure behind the retina called the Tapetum that can be observed on a veterinary eye exam by 6 to 16 weeks of age. Rod photoreceptor cells degenerate first resulting in loss of peripheral vision and night vision. As the disease progresses, cone photoreceptor cells also degenerate resulting in complete blindness. Most affected dogs are completely blind by 1 year of age, but some may retain limited sight until 3 to 4 years of age.
Genetic testing of the PDE6A gene will reliably determine whether a dog is a genetic Carrier of Progressive retinal Atrophy, Rod-cone dysplasia 3. Progressive retinal atrophy, Rod-cone dysplasia 3 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 being a carrier of the PDE6A 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. However, because there are multiple types of PRA caused by mutations in other genes, a normal result in PDE6A does not exclude PRA in a pedigree.
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.
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