Dilated cardiomyopathy (DCM) is a complex, life-threatening disorder of weak and thin heart. It is characterized by left ventricular dilation and systolic dysfunction with subsequent development of both atrial and ventricular tachyarrhythmias, which can result in the development of congestive heart failure and sudden cardiac death due to its decreased ability to pump blood. The clinical signs include exercise intolerance, persistent coughing, weakness, weight loss, breathing difficulties, fainting and swelling of the abdomen. DCM is a serious disorder and while there is no cure, the affected dogs can receive therapies to control arrhythmias, improve the heart’s function and manage congestive heart failure to manage the progression of the disorder and optimising quality of life.
DCM is associated with 4 different risk variants. DCM1 and DCM2 mutations are both dominantly inherited and are mostly present in the USA, meanwhile the two of the following mutations, DCM3 and DCM4, are mostly present in Europe, with DCM3 following a dominant inheritance pattern and DCM4 following a recessive inheritance pattern. The results of genetic testing indicated that DCM1 and DCM2 are associated linkage markers for DCM in USA Dobermans and that DCM3 and DCM4 are highly associated linkage markers for DCM in European Dobermans, meanwhile DCM1/DCM2 have been shown to have no association with risk in European Dobermans.
DCM is a disorder of multifactorial nature, which means that there is no exact genetic risk factor and there may also be other genetic or environmental factors affecting development and progression of the disease. There is also no apparent difference in clinical severity between dogs affected by either of one mutation, with all of the affected dogs developing the disease by the age of 6 years. However, there is a protentional higher risk of developing DCM if a dog is carrier or affected by two or more combinations of risk variants.
For USA Dobermans: Risk of dogs developing a DCM based on inheritance of both variants DCM1 and DCM2 is considered higher than in those clear of either risk variant. However, not all dogs with the variants will develop DCM, so the variants are of incomplete penetrance.
For the European Dobermans: Risk of developing a DCM based on inheritance of DCM3 and DCM4 risk variants (for better understanding look at the table below). Note that DCM4 has a stronger influence on risk compared to DCM3.
Genotype / risk | DCM4 clear | DCM4 carrier | DCM4 affected |
DCM3 clear | low risk | low risk | high risk |
DCM3 carrier | medium risk | medium risk | high risk |
DCM3 affected | high risk | high risk | highest risk |
For breeders: Given limited number of clear dogs for DCM variants, breeders should focus on gradually reducing the frequency of highest-risk dogs over several generations to safely pass the good genetics and features on to future litters while eliminating the risk of developing a DCM. However, this approach carries the risk of overusing certain sires, creating population bottlenecks and reducing genetic diversity within the breed.
Inheritance: complex
Mutation: PDK4, TTN, SNP on chromosome 5, RNF207
Genetic test: The method used for testing is extremely accurate and allows complete differentiation between affected animals, carriers and healthy dogs. Testing can be done at any age.
