Myotonia congenita

From Wikipedia, the free encyclopedia

Myotonia congenita is a genetic, neuromuscular disorder characterized by the slow relaxation of the muscles. Symptoms may include muscle stiffness and hypertrophy (enlargement). The disorder is caused by a genetic mutation involving the chloride channel of the muscles. The muscle stiffness, which particularly occurs in the leg muscles, may be enhanced by cold and inactivity, and is often relieved by exercise.

Historically two forms of myotonia congenita have been classified. The less severe form has been termed Thomsen myotonia congenita and is inherited in a dominant fashion; the more severe form has been termed Becker myotonia congenita and is inherited in a recessive fashion. More recently, as the individual mutations that give rise to this condition have been identified, these classifications are less widely used. The onset of the myotonia congenita is typically before the age of 20; most cases of myotonia congenita are nonprogressive and relatively nonlimiting.

It is important to note that involuntary twitches in skeletal muscle may not be caused by myotonia congenita as a far more common cause is fasciculation arising from benign fasciculation syndrome.

Goats of the "fainting goat" breed all suffer from this condition.

[edit] Treatment

Some cases of myotonia congenita do not require treatment. If necessary, however, symptoms of the disorder may be relieved with quinine, phenytoin and other anticonvulsant drugs. Physical therapy and other rehabilitative measures may also be used to help muscle function. Genetic counseling is available.