Common Symptoms
Dilated cardiomyopathy (DCM) is an inherited disorder of heart muscle affecting dogs. Affected dogs present with clinical signs of poor heart function before 3 years of age. Affected male dogs typically develop disease earlier than affected females, at around 1.5 years old versus 2.4 years old. Development of progressive cardiac muscle weakness, dilation of heart chambers, and thinning of heart walls result in poor contractility and makes affected dogs prone to potentially fatal arrhythmias. Affected dogs develop clinical signs ranging from exercise intolerance, fatigue, coughing, difficulty breathing, rapid breathing, fainting, collapse, and sudden death. Affected dogs that do not die suddenly from arrhythmias usually die from congestive heart failure when heart muscle becomes too weak to adequately pump blood. Different disease genes and environmental factors play a role 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 Giant Schnauzer
The Mutation of the RBM20 gene associated with dilated cardiomyopathy (schnauzer type) has been identified in the Giant Schnauzer, although its overall frequency in this breed is unknown.
Testing Tips
Genetic testing of the RBM20 gene in Giant Schnauzers will reliably determine whether a dog is a genetic Carrier of dilated cardiomyopathy (schnauzer type). Dilated cardiomyopathy (schnauzer type) 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 RBM20 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms may not appear until adulthood, 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 known carriers to each other is not recommended. Giant Schnauzers 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.
References
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Gilliam D (2016). Molecular Genetic Studies of Canine Inherited Diseases Including SAMS, Neuronal Ceroid Lipofuscinosis and Dilated Cardiomyopathy. (Ph.D. Dissertation). University of Missouri, Columbia, Missouri. Retrieved from https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/56525/research.pdf?sequence=2&isAllowed=y [Not in PubMed]
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Harmon MW, Leach SB, Lamb KE. Dilated Cardiomyopathy in Standard Schnauzers: Retrospective Study of 15 Cases. J Am Anim Hosp Assoc. 2017 Jan/Feb;53(1):38-44.
[PubMed: 27841675]
