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:
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).