What is Dilated Cardiomyopathy in Dobermans?
Dilated Cardiomyopathy (DCM) is the second most common heart disease in dogs, and is particularly well known among Doberman Pinschers. It can be a life-threatening condition in which the walls of the heart become thin and weak, leading to heart enlargement and eventual heart failure due to a decreased ability to pump blood. Onset of Doberman DCM typically occurs in adulthood after breeding has taken place, often in middle-to older-aged dogs. Due to this timing, research and the ability to screen for this condition are crucial for the health of future generations.
Symptoms of DCM can vary and may include exercise intolerance, persistent coughing, breathing difficulties, fainting, or swelling of the abdomen due to fluid build-up (known as ascites). Some dogs may only experience heart arrhythmias (irregular heartbeats) which can cause sudden death without other symptoms.
DCM is a complex disorder. Its development can be influenced by hereditary and non-hereditary factors–many of which to date are unknown. The risk variants tested by Wisdom are just a few of the considerations for understanding a dog’s unique predisposition to developing dilated cardiomyopathy.
What to expect if your dog is at risk
Dogs at risk of developing DCM should be examined at least once a year by a veterinarian and, if possible, a veterinary cardiologist. As an incurable and progressive condition, the focus of DCM treatment is tailored towards slowing progression, minimizing disease signs, and optimizing quality of life. An echocardiogram (heart ultrasound) may be used to understand the heart’s current health status. A portable electrocardiogram (ECG), known as Holter monitoring, may be used for asymptomatic dogs since arrhythmias can be the first–or only–clinical sign.
While the science continues to progress, dilated cardiomyopathy remains a serious and fatal disorder. Dogs who develop the disease receive therapy to control arrhythmias, improve the heart’s function and, if necessary, manage congestive heart failure. In addition, working with a veterinarian on appropriate diet and exercise plans can help improve quality of life. And, because stress can worsen clinical signs, keeping dogs as calm and stress-free as possible can be beneficial. However, the general prognosis for Dobermans who develop DCM is considered poor, with these individuals experiencing significantly shortened lifespans.
Scientific insights: DCM1 & DCM2
The development of DCM is a complex disorder that is likely both polygenic (influenced by multiple genes) and multifactorial (influenced by genetic and non-genetic factors). In humans, it’s reported that there are over 60 different genes associated with inherited dilated cardiomyopathy, and more still to be discovered.
In dogs—specifically Dobermans—two possible genetic risk factors have been identified by Dr. Kate Meurs and the team at North Carolina State University. The first, called DCM1, is a variant in the PDK4 gene. The DCM1 risk variant has been associated with heart disease in family lines of American Dobermans, with an estimated 37% of dogs with one or two copies of the variant developing DCM. The second variant, known as DCM2, is in the TTN gene. It is estimated that 50% of dogs with one or two copies of DCM2 develop the condition. However, Dobermans with both DCM1 (one or two copies) and DCM2 (one or two copies) are considered at highest risk, with an estimated 60% likely to develop DCM.
It’s important to note that, outside the original studies, DCM1 and DCM2 risk variants have not been associated with DCM diagnosis in other Doberman subpopulations–including European Dobermans–or in other dog breeds. These findings have been substantiated by separate subsequent studies, Owczarek-Lipska et al. (2013) and Niskanen et al. (2023).
More recently, Wisdom’s team of expert scientists have partnered with the Finnish University of Helsinki in their efforts to study Doberman DCM. The findings–outlined in the largest publication on this topic to date–identified two additional genetic risk variants associated with the development of DCM in European Dobermans. These variants are termed DCM3, the minor risk variant, and DCM4, the major risk variant, and are included in select Wisdom Panel dog DNA tests. For more information, check out our blog: Doberman DCM3 & DCM4.
It is important to note that the four currently tested variants do not explain all occurrences of DCM in the breed, suggesting additional genetic factors may be involved. Thus, further research is needed to understand the full risk profile in Dobermans, as well as additional studies to understand the relevant risk to Dobermans of various regions regarding the newly discovered DCM3 and DCM4 variants. Be sure to check out the end of this post to see how you may be able to contribute to the understanding of Doberman DCM.
Technical genetic details
The DCM1 and DCM2 variants are considered autosomal dominant, meaning only one copy (of either) needs to be present for a dog to be at increased risk. They are considered “risk variants” due to having incomplete penetrance or, in other words, not all dogs with the variant(s) will go on to develop heart disease. However, if bred, they can pass the risk variant(s) to their puppies.
The following is the conventional genotype format for each variant:
DCM1, PDK4 gene variant
0 copy (clear) = n/n
1 copy (heterozygous) = n/DCM1
2 copies (homozygous) = DCM1/DCM1
DCM2, TTN gene variant
0 copy (clear) = n/n
1 copy (heterozygous) = n/DCM2
2 copies (homozygous) = DCM2/DCM2
Breakdown of risk by genotype
The risk for developing DCM is considered to vary based on the combination of inherited variants. Meaning, dogs with one copy of a single variant are considered at higher risk than those clear of either risk variant, and dogs who inherit both variants are considered at highest risk.
While the exact risk level for each category has not been scientifically published, the following has been proposed by the NCSU team who first identified the variants:
- 37% of Dobermans with one or two copies of the DCM1 risk variant will develop DCM
- 50% of Dobermans with one or two copies of the DCM2 risk variant will develop DCM
- 60% of Dobermans with one or two copies of the DCM1 variant and one or two copies of the DCM2 variant will develop DCM
Please be mindful that as research into risk factors for developing Doberman DCM continues, our understanding of these risk variants may also change.
Breeding recommendations
Given the frequency of DCM within the breed, it is essential that breeding away from the risk variants is done gradually to maintain genetic diversity within the Doberman breed. It would be damaging to the breed population to try to solve the issue in a single generation.
Therefore, it is recommended to select mating pairs based on genotypes so that high-risk genotypes are avoided in the offspring and weight is given to family lines that have low clinical expression of DCM. Dogs carrying one copy of a single variant (DCM1 or DCM2), or dogs with two copies of a single variant and a low rate of family members diagnosed with DCM, shouldn’t be excluded from breeding and, ideally, paired with a dog clear of either variant. To ensure that none of the resulting puppies are in the highest risk category, it is important to avoid outcomes where dogs could inherit both DCM1 and DCM2. Subsequent generations should be tested before choosing breeding pairs to responsibly manage the condition in the breed and gradually work towards decreasing its incidence.
Most importantly, please keep in mind the complex development of Doberman DCM is still undergoing research. For detailed information on DCM3 and DCM4 variants, please check out the accompanying information on our DCM breeder page. The information shared in this post should not discourage using imported lines to maintain breed diversity.
Next steps in genetic research
The Wisdom team is always ready to take the science further. We are currently seeking participants for a study to review the association of DCM3 and DCM4 with the development of DCM in North American Doberman family lines. Additionally, the study will provide further insight between the interactions of the four described DCM risk variants in the given Doberman population.
For more information on the study, including inclusion criteria and the application process, please visit our DCM in Dobermans page.
