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Juvenile Dilated Cardiomyopathy (Discovered in the Toy Manchester Terrier)

Juvenile Dilated Cardiomyopathy (JDCM) is a heart condition that results in the sudden death of puppies and young dogs. The associated genetic variant has been identified in the Toy Manchester Terrier.

Found in

1 in 3,700 dogs

in our testing

Key Signs

Asymptomatic dilated cardiomyopathy, Sudden death, Cryptorchidism

Age of Onset

0 to 2 yrs

Juvenile onset


Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with JDCM

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about JDCM

Juvenile Dilated Cardiomyopathy is a type of heart disease described in Toy Manchester Terriers. Affected dogs typically appear healthy with no overt signs of heart disease before experiencing sudden cardiac death at a young age. Reported ages of death range from as early as 10 weeks to as late as 1 year. Several affected puppies were reported to pass within a day of undergoing general anesthesia or following exercise. Death is presumed to be the result of a sudden fatal arrhythmia. Post-mortem examination of affected dogs may show mild enlargement and dilation of the heart. Other post-mortem findings may include degeneration and scarring of heart tissue and varying degrees of inflammation. Affected male puppies may also demonstrate unilateral or bilateral cryptorchidism.

Dogs that are at risk of developing JDCM should be routinely examined by a veterinary cardiologist. Holter monitors may be used for asymptomatic dogs since cardiac arrhythmias may be the first clinical sign of dilated cardiomyopathy. As there is no curative treatment for JDCM, therapy is guided to addressing sequelae of heart disease. Clinical signs may vary among affected dogs and treatment should be optimized for the individual dog. Treatment options may include anti-arrhythmic medications and medications treating cardiac failure. Owners should be instructed to reduce and avoid stress in affected dogs, as stress can exacerbate clinical signs.

For Breeders

Planning to breed a dog with this genetic variant?

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.

This disorder is autosomal recessive, meaning two copies of the variant are needed for a dog to be at an elevated risk for being diagnosed with the condition. A carrier dog with one copy of the Juvenile Dilated Cardiomyopathy (Discovered in the Toy Manchester Terrier) variant can be safely bred with a clear dog with no copies of the Juvenile Dilated Cardiomyopathy (Discovered in the Toy Manchester Terrier) variant. About half of the puppies will have one copy (carriers) and half will have no copies of the variant. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disorder signs similar to the ones associated with this Juvenile Dilated Cardiomyopathy variant could develop due to a different genetic or clinical cause.

Technical Details

Technical details are not available at this moment.