Myotonia congenita is an autosomal recessive disorder of ion channel function in muscle fibers. It is characterized by slow and delayed relaxation of skeletal muscles after sudden contraction, due to chemical blockade of ion conductance and reflects a state of muscle fiber hyperexcitability. This is typically provoked by gait initiation or sudden movements after rest.

The clinical signs of affected dogs occur at around 3 months of age.  The main clinical signs include skeletal muscle hypertrophy, muscle stiffness, stiff gait, difficulty in swallowing, excessive salivation, noisy breathing (stridor) and troubled breathing (dyspnea). The severity of myotonia improves after continued activity as the so-called warm-up phenomena.

Inheritance: autosomal recessive - read more

Mutation:  CLCN1  gene

References (OMIA): https://www.omia.org/OMIA000698/9615/

Genetic test: The method used for genetic testing is extremely accurate and allows complete differentiation between affected animals, carriers and healthy dogs. DNA testing can be done at any age. 

Disease control: read more

DNA test sample: EDTA whole blood (1.0 ml) or buccal swabs. Detailed information about sampling can be found here.