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Myotonia congenita


Definition:

Myotonia congenita is an inherited condition that affects muscle relaxation. It is congenital, meaning that it is present from birth.

Alternative Names:

Thomsen's disease; Becker's disease

Causes:

Myotonia congenita is caused by a genetic change (mutation). It is passed down from either one or both parents to their children (inherited).

Myotonia congenita is caused by a problem in the part of the muscle cells that are needed for muscles to relax. Abnormal repeated electrical signals occur in the muscles, causing a stiffness called myotonia.

Symptoms:

The hallmark of this condition is myotonia -- the muscles are unable to quickly relax after contracting. For example, after a handshake, the person is only very slowly able to open and pull away his hand.

Early symptoms may include:

  • Difficulty swallowing
  • Gagging
  • Stiff movements that improve when they are repeated
  • Shortness of breath or tightening of the chest at the beginning of exercise

Children with myotonia congenita often look muscular and well-developed. They may not have symptoms of myotonia congenita until age 2 or 3.

Exams and Tests:

The doctor may ask if there is a family history of myotonia congenita.

Tests include:

Treatment:

Mexiletine is a medication that treats symptoms of myotonia congenita. Other treatments include:

  • Phenytoin
  • Procainamide
  • Quinine
  • Tocainide
Outlook (Prognosis):

People with this condition can do well. Symptoms only occur when a movement is first started. After a few repetitions, the muscle relaxes and the movement becomes normal.

Some people experience the opposite effect (paradoxical myotonia) and get worse with movement. Their symptoms may improve later in life.

Possible Complications:
  • Aspiration pneumonia caused by swallowing difficulties
  • Frequent choking, gagging, or trouble swallowing in an infant
  • Long-term (chronic) joint problems
  • Weakness of the abdominal muscles
When to Contact a Medical Professional:

Call your health care provider if your child has symptoms of myotonia congenita.

Prevention:

Couples who want to have children and who have a family history of myotonia congenita should consider genetic counseling.

References:

Bernard G, Shevell MI. Channelopathies: a review. Pediatr Neurol. 2008;38:73-85.

Chinnery PF. Muscle diseases. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 429.

Kerchner GA, Lenz RA, Ptacek LJ. Channelopathies: Episodic and electrical disorders of the nervous system. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, PA: Butterworth-Heinemann: 2008:chap 68.


Review Date: 2/20/2014
Reviewed By: Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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