Myotonia congenita

Alternative names:

Thomsen's disease

Symptoms:

The hallmark of myotonia congenita is the myotonia which is the inability of the muscle to relax quickly after voluntary relaxation has been initiated. This is exemplified by a handshake in which 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 muscle are slow to relax. Initial movements may be stiff but improve with immediate repetition. Children with myotonia congenita often appear muscular and well developed.
SYMPTOMS & EASILY RECOGNIZABLE SIGNS

• a family history of myotonia congenita
• slow relaxation of muscles following voluntary relaxation
• gagging
• swallowing difficulties
• difficulty initiating a movement but repetitive movement becomes easier

Note: The disorder may not show symptoms until the child is 2 or 3 years old.

Signs and tests:

There is often a family history of myotonia congenita.

An EMG demonstrates myotonic potentials.
A muscle biopsy shows increased diameter of individual muscle fibers.