Stargardt Disease

Other Names: Juvenile Macular Degeneration, STGD
Affected Genes: ABCA4
Inheritance: Autosomal Recessive
Mutation: chr6:55146556-55146557: 1 bp insertion (ins C)

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Common Symptoms

Stargardt disease is an inherited eye disease affecting dogs. Stargardt disease is caused by the degeneration of both Rod and cone type Photoreceptor Cells of the Retina. These are important for vision in dim and bright light, respectively. Affected dogs present prior to 10 years of age with signs of vision loss including dilated pupils and decreased response to light. On a veterinary eye exam, affected dogs will have changes in reflectivity and appearance of a structure behind the retina called the Tapetum and, may show thinning of the retinal blood vessels. Dogs may not completely lose their vision during their lifetime, but will develop significant loss of vision, especially in well-lit environments.


Breed-Specific Information for the Australian Labradoodle

The Australian Labradoodle is included as a breed susceptible to Stargardt Disease because of its close relatedness to the Labrador Retriever, which is known to develop this disease due to Mutation of the ABCA4 gene. The frequency of the causal mutation in the general Australian Labradoodle population is unknown.


Testing Tips

Genetic testing of the ABCA4 gene in Australian Labradoodles will reliably determine whether a dog is a genetic Carrier of Stargardt disease. Stargardt Disease is inherited in an Autosomal Recessive manner in dogs. This means 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 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 ABCA4 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. To eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding known carriers to each other is not recommended. Australian Labradoodles that do not carry the mutation have no increased risk of having affected pups.


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

  • Makelainen S, Godia M, Hellsand M, Viluma A, Hahn D, Makdoumi K, Zeiss CJ, Mellersh C, Ricketts SL, Narfstrom K, Hallbook F, Ekesten B, Andersson G, Bergstrom TF. An ABCA4 loss-of-function mutation causes a canine form of Stargardt disease. [PubMed: 30889179]