Myotonia Congenita (Labrador Retriever Type)

Other Names: MC
Affected Genes: CLCN1
Inheritance: Autosomal Recessive
Mutation: chr16:6077509 (canFam4): T/A
Breed(s): Australian Labradoodle, Labradoodle, Labrador Retriever

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Common Symptoms

Myotonia Congenita is an inherited musculo-skeletal disorder affecting dogs. Affected dogs can present as early as 8 weeks of age with a stiff-legged gait. Increased respiratory sounds may occur when the dog becomes excited, and dogs may have difficulty swallowing food and water. In later stages of disease, affected dogs may collapse with a rigid body and extended limbs. Affected dogs recover from collapse quickly and may show gait improvements with prolonged activity. These signs are caused by abnormal electrolyte channels in the muscles. Dogs with a mild presentation may live a normal life, while more severe presentation may require medical treatment with varied success.

Testing Tips

Genetic testing of the CLCN1 gene in dogs will reliably determine whether it is a genetic Carrier of Myotonia congenita (Labrador Retriever Type). This disease is inherited in an Autosomal Recessive manner. This means that dogs 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 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 CLCN1 gene mutation. Reliable genetic testing is important for determining breeding practices. To eliminate this mutation from breeding lines and avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that do not carry the mutation are not at 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.


  • Quitt PR, Hytönen MK, Matiasek K, Rosati M, Fischer A, Lohi H. Myotonia congenita in a Labrador Retriever with truncated CLCN1. Neuromuscul Disord. 2018 Jul;28(7):597-605. [PubMed: 29934119]