Common Symptoms
Polyneuropathy (Leonberger and Saint Bernard type) is an inherited neurologic disease affecting Leonbergers. Affected dogs most commonly present before 3 years of age with signs of generalized neurologic disease including weakness, loss of muscle tone, muscle Atrophy, awkward high-stepping gait in the hind limbs, decreased reflexes, abnormal bark sounds and increased breathing sounds due to paralysis of the larynx. With time, the disease may progress to the point that affected dogs are unable to bear weight or walk. Although published reports indicate that this is an Autosomal Recessive condition in most dogs, meaning that two copies of the Mutation are required for a dog to be affected, some dogs with a single copy of the mutation (carriers) may also be at-risk of developing the disease.
Breed-Specific Information for the Leonberger
The Mutation of the ARHGEF10 gene associated with polyneuropathy (Leonberger and Saint Bernard type) has been identified in Leonbergers. Though the exact frequency in the overall Leonberger population is unknown, approximately 15.4% out of 4074 non-randomly selected Leonbergers tested from North America and Europe were carriers of the mutation and 1.3% were at-risk. Leonbergers without the ARHGEF10 gene mutation have been diagnosed with polyneuropathy indicating that there are likely other genetic or environmental factors in Leonbergers that may cause this disease. It has been estimated that this mutation is responsible for causing approximately 20% of all Leonberger polyneuropathy cases.
Testing Tips
Genetic testing of the ARHGEF10 gene in Leonbergers will reliably determine whether a dog is a genetic Carrier of polyneuropathy (Leonberger and Saint Bernard type). Polyneuropathy 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. Though it is reported to be unlikely, it has not been determined whether or not dogs inheriting only a single copy of the Mutation (carriers) develop disease. Carrier dogs that are bred with another carrier of the same mutation are at 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 of the ARHGEF10 mutation and, in either case, may be susceptible to polyneuropathy. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood in some cases, 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. Leonbergers 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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Ekenstedt KJ, Becker D, Minor KM, Shelton GD, Patterson EE, Bley T, Oevermann A, Bilzer T, Leeb T, Drögemüller C, Mickelson JR. An ARHGEF10 deletion in highly associated with a juvenile-onset inherited polyneuropathy in Leonberger and Saint Bernard dogs. PLoS Genet. 2014 Oct 2;10(10):e1004635.
[PubMed: 25275565]
