Myotonia Congenita

Myotonia congenita is a genetic, neuromuscular disorder. It causes slow relaxation of the muscles.


It is caused by a genetic mutation. This involves the chloride channel of the muscles.


Symptoms may include muscle:

  • Stiffness.

  • Enlargement (hypertrophy).

The stiffness often happens in the leg muscles. It may be enhanced by cold and inactivity. It is often relieved by exercise.


Most cases do not require treatment.

  • Sometimes, symptoms may be relieved with anticonvulsant drugs.

  • Physical therapy and other rehabilitative measures may be used to help muscle function.

  • Genetic counseling is available.

Most cases are not progressive. They are relatively nonlimiting. A precise diagnosis allows caregivers to distinguish the mild form (Thomsen type) from the more severe form (Becker type).