Common Symptoms
Dilated cardiomyopathy (DCM) is an inherited disorder of the heart affecting dogs. 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 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. Affected dogs develop clinical signs as they age 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.
Testing Tips
Genetic testing of the TTN gene will reliably determine whether a dog is a genetic Carrier of the TTN Mutation associated with dilated cardiomyopathy. Dilated cardiomyopathy due to this mutation is inherited in an Autosomal Dominant manner 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 at least a 50% chance of inheriting one copy of the TTN 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. Dogs that are not carriers of the mutation have no increased risk of having affected pups due to this mutation.
The TTN mutation is the second mutation that has been associated with DCM in the Doberman pinscher. The first mutation, discovered in the PDK4 gene, is also inherited in a dominant manner with incomplete Penetrance. Dogs inheriting both known mutations in TTN and PDK4 are at even greater risk of developing DCM than those inheriting either one of the DCM-associated mutations alone. According to investigators, approximately 47% to 50% of dogs that have inherited the TTN mutation alone will develop DCM compared to 37% of dogs that have inherited the PDK4 mutation alone. Most concerningly, approximately 60% of dogs that have inherited at least one copy of both mutations are expected to develop DCM.
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
-
Meurs KM (2016) Doberman DCM Update & DCM2 Gene – Webinar: https://mymediasite.online.ncsu.edu/online/Play/d84281e7f40643bd84d96f0755f0cb9b1d
-
Meurs KM, Friedenberg SG, Kolb J, Saripalli C, Tonino P, Woodruff K, Olby NJ, Keene BW, Adin DB, Yost OL, DeFrancesco TC, Lahmers S, Tou S, Shelton GD, Granzier HG. A missense variant in the titin gene in Doberman pinscher dogs with familial dilated cardiomyopathy and sudden cardiac death. Hum Genet. 2019 May;138(5):515-524. doi: 10.1007/s00439-019-01973-2.
[PubMed: 30715562]
