The disorder may not show symptoms until the child is 2 or 3 years old. An EMG demonstrates myotonic potentials. A muscle biopsy shows increased diameter of individual muscle fibers. No treatment is available for myotonia congenita. Procainamide or quinidine sulfate may partially relieve the symptoms.
Affected people do well.
Symptoms only occur when a movement is first started. After a few repetitions, the muscle relaxes and the movement becomes normal. Symptoms may improve later in life. Call for an appointment with your health care provider if symptoms of myotonia congenita develop.