Common Symptoms
Progressive retinal Atrophy, X-linked 2 (XLPRA2) is an eye disease affecting dogs. Affected dogs may present with vision problems by 8 weeks of age. Initial clinical signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the Retina called the Tapetum that can be observed on a veterinary eye exam. Progression of the disease leads to thinning of the retinal blood vessels, signifying decreased blood flow to the retina. Affected dogs initially have vision loss in dim light (night blindness) and loss of peripheral vision, which may progress to complete blindness. Due to its X-Linked Inheritance, male dogs are more frequently affected with this disease than female dogs.
Testing Tips
Genetic testing of the RPGR gene will reliably determine whether a dog is a genetic Carrier of progressive retinal Atrophy, X-linked 2. This disease is inherited in an X-linked manner in dogs meaning that female dogs must receive two copies of the mutated gene (one from each parent) to develop the disease while male dogs only require one copy of the mutated gene from the mother in order to develop the disease. Therefore, male dogs more commonly present with symptoms of the disease. Each male pup that is born to a female dog known to be a carrier of RPGR has a 50% chance of inheriting the disease. 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. Female 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 RPGR 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.
References
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Beltran WA, Hammond P, Acland GM, Aguirre GD. A frameshift mutation in RPGR exon ORF15 causes photoreceptor degeneration and inner retina remodeling in a model of X-linked retinitis pigmentosa. Invest Ophthalmol Vis Sci. 2006 Apr;47(4):1669-81.
[PubMed: 16565408]
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Zangerl B, Johnson JL, Acland GM, Aguirre GD. Independent origin and restricted distribution of RPGR deletions causing XLPRA. J Hered. 2007;98(5):526-30.
[PubMed: 17646274]
