Stargardt Disease

Description

Stargardt Disease is an autosomal recessive disorder found in Labrador Retrievers that affects a dog’s ability to see. The disease is caused by a mutation in the ABCA4 gene that leads to the production of a shorter protein that is thought to be toxic to photoreceptors in the retina. This leads to the degeneration of the rods and cones in a dog’s eye over time, impairing its vision in dim and bright light, respectively.
The disease tends to start affecting dogs between 7 and 10 years old, but symptoms can present earlier. Clinically, the disease is characterized by a change in shape and reflectivity of the Tapetum, which is a structure behind the retina. Blood vessels in the retina may also become thin. Symptoms include a significant loss in vision, especially in well-lit areas.
Stargardt Disease is a recessive disorder, so a dog must have two copies of the defective gene (one from each parent) to have symptoms. A dog that carries one copy of the mutation does not exhibit any symptoms, but they can still pass on a copy of the mutation to their offspring. If two carrier dogs produce a litter of puppies, each puppy has a 25% chance of being affected by Stargardt Disease.
 

References

References: PLOS Genetics. 2019; vol. 15, no. 3. An ABCA4 Loss-of-Function Mutation Causes a Canine Form of Stargardt Disease. Mäkeläinen, Suvi, et al.