Myotonia Congenita is an inherited musculo-skeletal disorder affecting dogs. Affected dogs can present as early as 8 weeks of age with a stiff-legged gait. Increased respiratory sounds may occur when the dog becomes excited, and dogs may have difficulty swallowing food and water. In later stages of disease, affected dogs may collapse with a rigid body and extended limbs. Affected dogs recover from collapse quickly and may show gait improvements with prolonged activity. These signs are caused by abnormal electrolyte channels in the muscles. Dogs with a mild presentation may live a normal life, while more severe presentation may require medical treatment with varied success.