Dilated Cardiomyopathy for Doberman Pinschers only, DCM3 risk variant (Linkage Test)

Dilated Cardiomyopathy is the second most common heart disease in dogs and is characterized by systolic dysfunction with left or biventricular dilation, normal to reduced wall thickness, and cardiomegaly (heart enlargement). More specifically, DCM in the Doberman Pinscher is characterized by left ventricular systolic dysfunction and secondary left ventricular enlargement, typically presenting in middle to older aged dogs. These changes result in the heart’s diminished ability to serve as a pump, leading to cardiac failure. The symptoms of cardiac failure are exercise intolerance, persistent cough, breathing difficulties, and ascites (fluid accumulation within the abdomen causing swelling). DCM is also characterized by arrhythmias, such as ventricular premature complexes (VPCs), which can cause sudden cardiac death without any previous symptoms. Dilated cardiomyopathy is a progressive condition in Dobermans, and the life expectancy of affected dogs can be significantly reduced. Clinical research indicates males tend to show echocardiographic changes earlier in life while females are more likely to have VPCs as the only abnormality. Genetic research has shown an association between two variants (DCM3 and DCM4) and development of DCM characterized by left ventricular systolic dysfunction and dilation in purebred European Dobermans. These risk variants are part of a complex genetic background and do not explain all occurrences of DCM in Dobermans, including those which develop VPCs, suggesting additional genetic factors may be involved. Further research is needed to understand the clinical relevance of these risk variants in American and other Doberman sub-populations as well as mixed breed dogs with Doberman ancestry identified in their breed background. In the European Doberman cohort studied to identify DCM3 and DCM4, no association was found between DCM and either the PDK4 (DCM1) variant or the TTN (DCM2) variant previously identified as risk factors for the condition in American Doberman family lines. Please note, the Wisdom tests for DCM3 and DCM4 are what is known as linkage testing. Linkage testing does not directly test for the causal variant but provides a prediction based on nearby associated marker(s) in the DNA.

Dogs that are at risk of developing DCM should be examined at least once yearly by a veterinary cardiologist. A full cardiac workup is recommended including chest radiographs (X-rays), an echocardiogram (heart ultrasound), and an electrocardiogram (ECG). Clinical signs may vary among affected dogs, and Holter monitoring can be used for asymptomatic dogs since arrhythmias can occur without other indications of disease. As there is no curative treatment, therapy should be optimized for the individual. Medical therapy may be implemented to improve the heart’s pumping ability, control heart rate, manage arrhythmias, and remove lung congestion if present. Owners should be instructed to reduce and avoid stress in affected dogs, as stress can exacerbate clinical signs. Unfortunately, DCM is a progressive condition and Dobermans tend to carry a worse prognosis than other breeds. The life expectancy of affected dogs is often significantly reduced. However, medical therapy may help improve quality of life and short-term prognosis in those who respond favorably.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

Four genetic risk factors for Dilated Cardiomyopathy in the Doberman Pinscher have been screened by this panel. The risk variants DCM1 and DCM2 have been associated with cardiomyopathy in American Doberman, but not European Doberman, and should therefore be considered for American Dobermans only. The risk variants DCM3 and DCM4 were identified in Dobermans within Germany and Finland, with further validation in samples from the Netherlands, Slovenia and Sweden. Thus, the variants are likely to be highly relevant for European Dobermans but currently of unknown relevance in other Doberman populations. However, this should not discourage using imported lines to maintain diversity. For risk profiling, the DCM3 and DCM4 risk variants should be considered together. Given the high prevalence of DCM3 and DCM4, it is essential that breeding away from these variants is done gradually to maintain genetic diversity within the breed. Therefore, we recommend selecting mating pairs to avoid high (AA/AA, AG/AA, GG/GG, GG/AG) and highest (GG/AA) risk genotype categories in the offspring. Subsequent generations should be genetically tested before choosing breeding pairs to responsibly manage the condition in the population and gradually work towards decreasing its incidence. The Wisdom tests for DCM3 and DCM4 are what is known as linkage testing. Linkage testing does not directly test for the causal variant but provides a prediction based on nearby associated marker(s) in the DNA. Please visit our website for further resources and breeder advice. Additionally, please note that these four genetic variants do not explain all occurrences of DCM in the breed, suggesting additional genetic factors may be involved. Further research is needed to understand the clinical relevance of DCM3 and DCM4 risk variants in American and other Doberman populations.