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Myotonia Congenita in Dogs

myotonia congenita in dogs

Myotonia congenita is an inherited skeletal muscle disorder. This condition is characterized by delayed relaxation of skeletal muscle without any symptoms of weakness or muscular breakdown.

Impacting certain breeds, such as Miniature Schnauzers, there are treatment options available to reduce symptoms. However, the diagnosis process can be costly.

What Is Myotonia Congenita in Dogs and Causes It?

Myotonia Congenita is a genetic muscle disorder that is seen in mice, goats, dogs, horses, humans, and other mammals. It is caused by mutations in the CLCN1 gene, which is responsible for encoding CL1C-1, a chloride channel protein.

In the case of myotonia congenita, this mutation leads to a shortened CIC-1 protein, which results in poor chloride conduction in the skeletal muscles of dogs.

Researchers have discovered genetic variants in the CLCN1 gene in select breeds. The common breeds impacted include Miniature Schnauzers and Chow Chows. However, isolated cases have also been reported in Great Danes, Cocker Spaniels, Jack Russell Terriers, Staffordshire Bull Terriers, and Australian Cattle Dogs.

Clinical Warning Signs of Myotonia Congenita

Unfortunately, dogs affected by myotonia congenita will typically showcase clinical signs at a few weeks of age.

Since this condition directly impacts skeletal muscles, the most common clinical signs include:

  • Stiff gait
  • Trouble getting up, particularly after a period of resting
  • Difficulty swallowing
  • Upper airway stridor (a high-pitched, wheezing sound caused by reduced airflow)
  • Swollen tongue (may notice that the tongue is protruding from the mouth)

While studying an 8 week old Labrador Retriever who displayed stiff-legged “robotic” gait, it was found that symptoms were most evident after rest and improved following prolonged activity. Occasionally, the dog would also collapse following sudden movements due to the rigidity of the trunk and limbs.

How Is Myotonia Congenita in Dogs Diagnosed?

To reach a diagnosis, a dog owner will need to provide a history of their dog’s health, including the onset of current symptoms. At this point, a physical examination will likely be recommended, in addition to potential laboratory testings, including a urinalysis and blood work.

Two of the most effective diagnostic methods include electromyography (EMG) and muscle biopsy (which will display symptoms of mild changes in the muscle). An EMG measures electrical impulses in the muscles and is particularly useful when aiming to diagnose myotonia congenita in dogs.

Genetic testing is now also available. Researchers recommend that breeding dogs be tested to limit the spread of this mutation, particularly among at-risk breeds.

What Options Are Available for Treating Myotonia Congenita in Dogs?

Sadly, there is no cure for this condition. However, if a dog is diagnosed with myotonia congenita, there are a number of medications available that will help stabilize the muscle cell membrane.

These medications will help better manage the associated symptoms and improve the dog’s quality of life, including:

  • Quinidine
  • Mexiletine
  • Procainamide

Receiving a definitive diagnosis can be expensive. It will also be important to schedule regular veterinarian visits to discuss your dog’s condition, particularly following the introduction of select medications.

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