Progressive Retinal Atrophy, Late-Onset (Lapponian Herder Type)

Other Names: Retinitis Pigmentosa, PRA
Affected Genes: IFT122
Inheritance: Autosomal Recessive
Mutation: chr20:5722348 (canFam4): C/T
Breed(s): Finnish Lapphund, Lapponian Herder

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Common Symptoms

Progressive Retinal Atrophy, Late-Onset (Lapponian Herder Type) is an eye disease affecting dogs. Affected dogs present with visual deficits at an average of 9 years 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.

Testing Tips

Genetic testing of the IFT122 gene will reliably determine whether a dog is a genetic Carrier of Progressive Retinal Atrophy, Late-Onset (Lapponian Herder Type). This disease 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 IFT122 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 progressive retinal atrophy caused by mutations in other genes, a normal result in IFT122 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

  • Kaukonen M, Pettinen IT, Wickström K, Arumilli M, Donner J, Juhola IJ, Holopainen S, Turunen JA, Yoshihara M, Kere J, Lohi H. A missense variant in IFT122 associated with a canine model of retinitis pigmentosa. Hum Genet. 2021 Nov;140(11):1569-1579. [PubMed: 33606121]