Progressive Retinal Atrophy, Rod-Cone Dysplasia 3

Other Names: Rod-cone dysplasia 3, PRA-rcd3
Affected Genes: PDE6A
Inheritance: Autosomal Recessive
Mutation: Deletion
Breed(s): Cardigan Welsh Corgi, Chinese Crested, Pembroke Welsh Corgi, Pomeranian

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Common Symptoms

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.


Testing Tips

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.


References

  • Corrigendum. Vet Ophthalmol. 2014 Jul;17(4):309-10.
  • Donner J, Kaukonen M, Anderson H, Moller F, Kyostila K, Sankari S, Hytonen M, Giger U, Lohi H. Genetic Panel Screening of Nearly 100 Mutations Reveals New Insights into the Breed Distribution of Risk Variants for Canine Hereditary Disorders. PLoS One. 2016 Aug 15;11(8):e0161005. [PubMed: 27525650]
  • Downs LM, Hitti R, Pregnolato S, Mellersh CS. Genetic screening for PRA-associated mutations in multiple dog breeds shows that PRA is heterogeneous within and between breeds. Vet Ophthalmol. 2014 Mar;17(2):126-30. doi: 10.1111/vop.12122. Epub 2013 Nov 21. [PubMed: 24255994]
  • Keep JM. Clinical aspects of progressive retinal atrophy in the cardigan Welsh corgi. Aust Vet J. 1972 Apr;48(4):197-9. [PubMed: 5082485]
  • Petersen-Jones SM, Entz DD, Sargan DR. cGMP phosphodiesterase-alpha mutation causes progressive retinal atrophy in the Cardigan Welsh corgi dog. Invest Ophthalmol Vis Sci. 1999 Jul; 40(8):1637-44. [PubMed: 10393029]
  • Petersen-Jones SM, Entz DD. An improved DNA-based test for detection of the codon 616 mutation in the alpha cyclic GMP phosphodiesterase gene that causes progressive retinal atrophy in the Cardigan Welsh Corgi. Vet Ophthalmol. 2002 Jun;5(2):103-6. [PubMed: 12071867]
  • Petersen-Jones SM, Zhu FX. Development and use of a polymerase chain reaction-based diagnostic test for the causal mutation of progressive retinal atrophy in Cardigan Welsh Corgis. Am J Vet Res. 2000 Jul; 61(7):844-6. [PubMed: 10895911]
  • Tuntivanich N, Pittler SJ, Fischer AJ, Omar G, Kiupel M, Weber A, Yao S, Steibel JP, Khan NW, Petersen-Jones SM. Characterization of a canine model of autosomal recessive retinitis pigmentosa due to a PDE6A mutation. Invest Ophthalmol Vis Sci. 2009 Feb; 50(2):801-13. [PubMed: 18775863]