Common Symptoms
Stargardt disease is a progressive inherited eye disease affecting dogs. Stargardt disease is caused by the 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 present prior to 10 years of age with signs of vision loss, including dilated pupils and decreased response to light. Affected dogs will have progressive changes in reflectivity and appearance of a structure behind the retina, called the Tapetum, that can be observed on a veterinary eye exam. Additionally, mild to moderate thinning of the retinal blood vessels may also be observed. However, signs of Stargardt disease are subtle in the first two years of life and may not be identified on early eye exams. Stargardt disease severity and speed of disease progression may vary. Dogs may not completely lose their vision during their lifetime, but will develop significant loss of vision, especially in well-lit environments.
Testing Tips
Genetic testing of the ABCA4 gene will reliably determine whether a dog is a genetic Carrier of Stargardt disease. Stargardt 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 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. 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.
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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Ekesten B, Mäkeläinen S, Ellis S, Kjellström U, Bergström TF. Abnormal Appearance of the Area Centralis in Labrador Retrievers With an ABCA4 Loss-of-function Mutation. Transl Vis Sci Technol. 2022 Feb 1;11(2):36. doi: 10.1167/tvst.11.2.36.
[PubMed: 35201338]
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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]
