Common Symptoms
Dilated Cardiomyopathy is an inherited disorder of the heart affecting several breeds of dog. This disease shows Incomplete Penetrance, meaning that not all dogs at risk (those with one or two copies of the Mutation) will develop the disease. In addition, in Doberman Pinschers, there may be more than one gene that causes dilated cardiomyopathy. In affected dogs, the heart muscle is weak and the chambers become dilated with thin walls. These enlarged hearts have poor contractility and are prone to arrhythmias. Affected dogs present with clinical signs of poor heart function between 1 to 8 years of age. As affected dogs age, they develop clinical signs ranging from mild exercise intolerance to sudden death or congestive heart failure. Signs of heart disease include exercise intolerance, fatigue, coughing, difficulty breathing, rapid breathing, fainting and sudden death. Affected dogs that don’t die suddenly from arrhythmias usually die from congestive heart failure around 7 years of age. Different disease genes and environmental factors play a role in the development of dilated cardiomyopathy in dogs. Therefore not all dogs with this disease will have the same genetic mutation.
Breed-Specific Information for the Doberman Pinscher
The Mutation of the PDK4 gene associated with dilated cardiomyopathy has been identified in the Doberman Pinscher. Though the exact frequency in the overall Doberman Pinscher population is unknown, 27% out of 66 unaffected Doberman Pinschers from the United States carried one copy of the mutation and 12% had two copies of the mutation. In a separate study in Europe, 18% out of 94 unaffected Doberman Pinschers from the United Kingdom and Germany carried one copy of the mutation and 5% had two copies of the mutation. Based on the scientific literature more than one gene is likely involved in this disease in Doberman Pinschers. Therefore, not all Doberman Pinschers with dilated cardiomyopathy will have one or two copies of this mutation. Due to Incomplete Penetrance, not all dogs with one or two copies of the mutation will develop dilated cardiomyopathy. Currently, the mutation in PDK4 is the only available molecular test for dilated cardiomyopathy. Dogs testing negative for this mutation may still be at risk for dilated cardiomyopathy based on pedigree or clinical history.
Testing Tips
Genetic testing of the PDK4 gene will reliably determine whether a dog is a genetic Carrier of the PDK4 Mutation associated with dilated cardiomyopathy. However, this mutation has only been identified as a cause of dilated cardiomyopathy in the Doberman pinscher. Dilated Cardiomyopathy due to this mutation is inherited in an Autosomal Dominant manner in Dobermans meaning that they only need to inherit one copy of the mutated gene to be at an increased risk of developing the disease. Each pup that is born to an affected dog has a 50% chance of inheriting one copy of the PDK4 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood and because the mutation shows Incomplete Penetrance, 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 Doberman pinschers known to have the mutation is not recommended (please see information below for breeds other than the Doberman pinscher). Dogs that are not carriers of the mutation have no increased risk of having affected pups due to this mutation.
*NOTE: The PDK4 gene mutation was originally identified in the Doberman pinscher and has only been associated with dilated cardiomyopathy in this breed. Though this mutation has been identified in several other breeds, including those known to develop dilated cardiomyopathy, a correlation between this mutation and dilated cardiomyopathy has not been established for these breeds. For this reason, dogs from breeds other than the Doberman pincher that have been found to have inherited this mutation should not be removed from breeding programs based upon the results of this genetic test alone. The most cautious approach for these dogs would be to make breeding decisions based upon cardiac exam results and recommendations from a board certified veterinary cardiologist.
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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Meurs KM, Lahmers S, Keene BW, White SN, Oyama MA, Mauceli E, Lindblad-Toh K. A splice site mutation in a gene encoding for PDK4, a mitochondrial protein, is associated with the development of dilated cardiomyopathy in the Doberman pinscher. Hum Genet. 2012 Aug; 131(8):1319-25.
[PubMed: 22447147]
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Owczarek-Lipska M, Mausberg TB, Stephenson H, Dukes-McEwan J, Wess G, Leeb T. A 16-bp deletion in the canine PDK4 gene is not associated with dilated cardiomyopathy in a European cohort of Doberman Pinschers. Anim Genet. 2013 Apr;44(2):239.
[PubMed: 22834541]
