Glycogen storage disease IIIa is an inherited metabolic disorder affecting dogs. Glycogen is the primary carbohydrate used by the body for energy. Affected dogs do not have sufficient enzymes to break down glycogen causing accumulation of glycogen in the liver and muscle. Though symptoms are mild in the first year of life and disease progression is variable, affected dogs typically present between one and two years of age with exercise intolerance, lethargy, vomiting, enlarged liver, and in some dogs, collapse with exercise secondary to low blood sugar. Progressive liver and muscle damage occur with age as glycogen continues to accumulate in cells.
Genetic testing of the AGL gene will reliably determine whether a dog is a genetic Carrier of glycogen storage disease IIIa. Glycogen storage disease IIIa 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 AGL gene mutation. Reliable genetic testing is important for determining breeding practices. 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.
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