Congenital myasthenic syndrome (CMS) is a congenital neuromuscular disease that leads to pronounced muscle weakness in affected dogs. The symptoms are particularly noticeable after physical activity, stress or excitement.

In addition to the Altdänischer Vorstehhund, Golden Retriever, Labrador Retriever, Jack Russell Terrier and Parson Russell Terrier breeds, the disease can now also be genetically identified in the Heideterrier. Puppies as young as a few days old can show signs of the disease: they have difficulty coordinating their forelegs and their reflexes are weakened or completely absent. General muscle weakness increases with age, especially during the day and at night.

A genetic test enables breeders to identify carrier animals at an early stage and plan breeding specifically to avoid affected offspring. The test can also be used to clarify a suspected diagnosis in dogs with corresponding clinical symptoms.