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Congenital Myasthenic Syndrome (Labrador Retriever Type)

Congenital myasthenic syndrome (CMS) is a genetic neuromuscular disease, primarily affecting Australian Cobberdog, Australian Labradoodle, Labradoodle, Labrador Retriever, UK Breed Council Labrador Retriever, characterized by severe exercise-induced limb weakness and a short-strided gait appearing around 2-3 weeks of age, often leading to early euthanasia due to the severity of the condition and lack of effective treatments.




Affected Genes: COLQ

Inheritance: Autosomal Recessive

Variant(canFam6):
chr23:27151083: T>C

Breed: Australian Cobberdog
Australian Labradoodle
Labradoodle
Labrador Retriever
UK Breed Council Labrador Retriever

General Information: Congenital myasthenic syndrome (CMS) is a hereditary neuromuscular disorder in dogs, typically manifesting at 2-3 weeks of age with severe, exercise-induced weakness in all four limbs leading to collapse. Affected dogs exhibit decreased reflexes and a short-strided gait that worsens with activity. Due to the severity of the condition, dogs may be humanely euthanized at a young age. Treatments for the similar acquired disorder, myasthenia gravis, are ineffective for CMS.

How to Read Your Dog's Test Results for this Genetic Variant:

Two Variants Detected: Dog Likely Affected

One Variant Detected: Dog Unlikely Affected

No Variants Detected: No Effect

Gene / Testing Information: Genetic testing for the COLQ gene can identify whether a dog is a carrier of congenital myasthenic syndrome (CMS). CMS is inherited in an autosomal recessive manner, meaning two copies of the mutated gene, one from each parent, are required for a dog to develop the disease. Carrier dogs typically do not show symptoms, but breeding two carriers together has a 25% chance of producing affected pups and a 50% chance of producing carriers. To prevent this, it is recommended not to breed known carriers together. Dogs that are not carriers of the mutation do not have an increased risk of having affected pups.

References:
Rinz CJ, Levine J, Minor KM, Humphries HD, Lara R, Starr-Moss AN, Guo LT, Williams DC, Shelton GD, Clark LA. A COLQ missense mutation in Labrador retrievers having congenital myasthenic syndrome. PLoS One 2014 9(8):e106425.

Shelton GD. Myasthenia gravis and congenital myasthenic syndromes in dogs and cats: A history and mini-review. Neuromuscul Disord. 2016 26(6):331-334.