Congenital Myasthenic Syndrome (Old Danish Pointer Type)

Other Names: CMS
Affected Genes: CHAT
Inheritance: Autosomal Recessive
Mutation: chr28:1484906 (canFam3): G>A
Breed(s): Old Danish Pointer

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Common Symptoms

Congenital myasthenic syndrome (Old Danish Pointer type) is an inherited Neuromuscular Disease affecting Old Danish Pointers. Clinical signs of exercise intolerance are noted in affected dogs between 12-16 weeks of age. Affected dogs can exercise and run normally for periods of 5 to 30 minutes. However, if exercising for longer periods of time, affected dogs will start running with progressively shorter strides until they eventually collapse. Dogs are able to recover from the transient paralysis after a few minutes of rest but if exercise is started again, symptoms will recur. The disease does not appear to progress in severity in affected dogs.

Testing Tips

Genetic testing of the CHAT gene will reliably determine whether a dog is a genetic Carrier of congenital myasthenic syndrome. Congenital myasthenic syndrome (Old Danish Pointer type) is inherited in an Autosomal Recessive manner in dogs meaning that they 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 that is 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 CHAT gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no 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.


  • Flagstad A, Trojaborg W, Gammeltoft S. Congenital myasthenic syndrome in the dog breed Gammel Dansk Hønsehund: clinical, electrophysiological, pharmacological and immunological comparison with acquired myasthenia gravis. Acta Vet Scand. 1989;30(1):89-102. [PubMed: 2782236]
  • Flagstad, A. A new hereditary neuromuscular disease in the dog breed "Gammel Dansk Honsehund". Genetic investigations. Hereditas. 1982; 96:211-4. [PubMed: 7201985]
  • Proschowsky HF, Flagstad A, Cirera S, Joergensen CB, Fredholm M. Identification of a mutation in the CHAT gene of Old Danish Pointing Dogs affected with congenital myasthenic syndrome. J Hered. 2007; 98(5):539-43. [PubMed: 17586598]