Myotonia congenitaDefinition: 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
Causes, incidence, and risk factors: Myotonia congenita is caused by a change (mutation) to a gene. It is passed down from either one or both parents to the children (inherited). Myotonia congenita is believed to be caused by a problem in the part of the muscle cells that are needed for muscles to relax. Abnormal repeated electrical discharges occur in the muscles, causing a stiffness called myotonia.
Symptoms: The hallmark of this condition is the myotonia -- the inability of the muscle 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: Children with myotonia congenita often appear to be muscular and well-developed. The child may not have symptoms of myotonia congenita until age 2 or 3.
Signs and tests: The doctor may ask if there is a family history of myotonia congenita. Tests include:
Treatment: Treatment for symptoms includes: - Mexiletine
- Phenytoin
- Procainamide
Expectations (prognosis): People can do well with this condition. 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: - Aspiration pneumonia caused by swallowing difficulties
- Frequent choking, gagging, or difficulty swallowing in an infant
- Abdominal muscle weakness
- Chronic joint problems
Calling your health care provider: Call your health care provider if your child has symptoms of myotonia congenita.
Prevention: Genetic counseling may be of interest to couples who want to have children and have a family history of myotonia congenita.
References: Barohn RJ. Muscle diseases. Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 447.
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