Skip navigation
MedlinePlus Trusted Health Information for You U.S. National Library of MedicineNational Institutes of Health
Contact Us FAQs Site Map About MedlinePlus
español Home Health Topics Drug Information Medical Encyclopedia Dictionary News Directories Other Resources

 

Medical Encyclopedia

Other encyclopedia topics:  A-Ag  Ah-Ap  Aq-Az  B-Bk  Bl-Bz  C-Cg  Ch-Co  Cp-Cz  D-Di  Dj-Dz  E-Ep  Eq-Ez  F  G  H-Hf  Hg-Hz  I-In  Io-Iz  J  K  L-Ln  Lo-Lz  M-Mf  Mg-Mz  N  O  P-Pl  Pm-Pz  Q  R  S-Sh  Si-Sp  Sq-Sz  T-Tn  To-Tz  U  V  W  X  Y  Z  0-9 

Myotonia congenita

Printer-friendly versionEmail this page to a friend
Contents of this page:

Illustrations

Superficial anterior muscles
Superficial anterior muscles

Alternative names    Return to top

Thomsen's disease

Definition    Return to top

Myotonia congenita is an inheritable congenital (present from birth) disorder characterized by slow relaxation of voluntary muscles, such as those in the legs.

Causes, incidence, and risk factors    Return to top

Myotonia congenita can be either an autosomal dominant or autosomal recessive disease. With the autosomal dominant form, a person only needs to inherit the mutation from one parent to be affected. Inheriting the recessive form means a person must inherit the mutation from both parents to be affected. The gene that causes this condition resides on chromosome 7.

The cause of myotonia congenita is believed to be an abnormality in the chloride channels of muscle cells (chloride ions are required for a muscle to relax). The abnormal chloride channels also cause an accumulation of potassium outside the cells and an activation of sodium channels in the muscle cells (sodium ions trigger muscle contraction).

When the cells have more than enough sodium but not enough chloride, abnormal repetitive electrical discharges cause a stiffness called myotonia.

Symptoms    Return to top

The hallmark of this condition is the myotonia -- the inability of the muscle to quickly relax after voluntary contraction. For example, after a handshake, the affected individual is only very slowly able to open and disengage his hand.

Early symptoms may include gagging and difficulty in swallowing, because oropharyngeal muscles are slow to relax. Initial movements may be stiff but improve with immediate repetition.

Children with myotonia congenita often appear to be muscular and well-developed. There may not be symptoms of myotonia congenita until the child is 2 or 3 years old.

Signs and tests    Return to top

Treatment    Return to top

Treatment for symptoms of myotonia congenita includes mexiletine, phenytoin, procainamide, and quinine.

Expectations (prognosis)    Return to top

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.

Complications    Return to top

Calling your health care provider    Return to top

Call your health care provider if symptoms of myotonia congenita develop.

Prevention    Return to top

Genetic counseling may be of interest to prospective parents with a family history of myotonia congenita.

Update Date: 4/25/2004

Updated by: Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network.

adam.com logo

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.