Genetic tests for mutations causing Congenital Myasthenic Syndrome in Labrador Retrievers and Jack Russell Terriers are now available in the MyDogDNA 2016 test panel. The disorder is considered severe, typically with an early onset of symptoms. See a more detailed description below.
Congenital Myasthenic Syndrome (CMS); mutation originally found in Labrador Retriever and mutation originally found in Jack Russell Terrier
Congenital Myasthenic Syndromes are a group of rare hereditary neuromuscular disorders. They are caused by abnormal signal transmission across the neuromuscular junction causing muscular weakness and lethargy of varying severity. CMS affects multiple dog breeds. The inheritance pattern is autosomal recessive.
In Jack Russell terriers, the disease is caused by deficiency of acetylcholine receptors in neuromuscular junctions. The typical symptom, severe muscular weakness after movement, is usually seen in puppies between 6-7 weeks of age. In the most severe cases the affected puppies can walk only 10-15 steps before collapsing.
In Labrador Retrievers, the disease is caused by the abnormal structure of the acethylcholinestrase enzyme in neuromuscular junctions. The symptoms are also typically seen in puppies between 6-7 weeks of age, and consist of severe muscular weakness after movement.