Progressive Retinal Atrophy (Basenji Type)

Other Names: Adult-onset progressive retinal atrophy, Basenji retinopathy
Affected Genes: SAG
Inheritance: Autosomal Recessive With Variable Expressivity
Mutation: Point Mutation
Breed(s): Basenji

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Common Symptoms

Progressive retinal Atrophy (basenji type) is an adult-onset inherited eye disease affecting basenjis. Affected dogs initially have changes in reflectivity and appearance of a structure behind the Retina called the Tapetum that is typically observed on a veterinary eye exam at around 5 years of age. Progression of the disease leads to thinning of the retinal blood vessels by 6 or 7 years of age, signifying decreased blood flow to the retina. Initial symptoms of disease in affected dogs include vision loss in dim light (night blindness) and loss of peripheral vision. The disease follows a variable progression and severity depending on the individual, but in many cases progresses to complete vision loss. Some affected dogs maintain vision in daylight for many years, sometimes for the remainder of their life.


Testing Tips

Genetic testing of the SAG gene in basenjis will reliably determine whether a dog is a genetic Carrier of progressive retinal Atrophy (basenji type). Progressive retinal atrophy (basenji type) 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 SAG gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood, genetic testing should be performed before breeding. 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 found to have this specific mutation have no increased risk of having affected pups. However, because there are multiple types of progressive retinal atrophy caused by mutations in other genes, a normal result in SAG does not exclude progressive retinal atrophy 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

  • Goldstein O, Jordan JA, Aguirre GD, Acland GM. A non-stop S-antigen gene mutation is associated with late onset hereditary retinal degeneration in dogs. Mol Vis. 2013 Aug 27;19:1871-84. eCollection 2013. [PubMed: 24019744]