Primary lens luxation is an inherited abnormality of the eye affecting bull terriers. It is characterized by dislocation of the lens in the eye due to the breakage of the ligaments (called zonules) that hold the lens in place. The age of onset is variable depending on whether a dog has one or two copies of the Mutation, but affected dogs typically present between 2 to 8 years of age with sudden signs of eye irritation. Symptoms of lens luxation include excessive blinking, squinting and tearing of the eye. Dislocation of the lens can occur in both the forward and backward position within the eye, but dislocation in the forward position is more common and serious. If not treated immediately, lens dislocation can lead to Glaucoma and vision loss.
Breed-Specific Information for the Bull Terrier
The Mutation of the ADAMTS17 gene associated with primary lens luxation has been identified in the bull terrier. Though the exact frequency in the overall bull terrier population is unknown, two out of seven bull terriers tested had one copy of the mutation and three had two copies of the mutation, for a total of 5 at risk dogs. PLL has been reported in bull terriers without this mutation, which suggests that other genes and/or environmental factors can play a role in the development of PLL in this breed.
Genetic testing of the ADAMTS17 gene in bull terriers will reliably determine whether a dog is a genetic Carrier of primary lens luxation. Primary lens luxation is inherited in an autosomal incomplete dominant manner in dogs meaning that dogs only need to inherit one copy of the mutated gene to be at an increased risk of developing the disease. Though lens luxation is most commonly seen in dogs having two copies of the mutated gene, carrier dogs have a low, but increased risk of lens luxation. Thus, dogs that have one or two mutant copies of the gene are considered at-risk for lens luxation. When a carrier of this Mutation is bred with another dog that also is a carrier of the same mutation, there is risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance that the puppy will inherit two copies of the mutation and a 50% chance that the puppy will inherit one copy of the mutation and, in either case, may be susceptible to lens luxation. Reliable genetic testing is important for determining breeding practices. Because symptoms may 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 is not recommended. Bull terriers that do not have the mutation have no increased risk of having affected pups when bred to a dog that is also clear for this mutation.
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.
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