Myotonia

Myotonia is muscle stiffness due to difficulty relaxing the muscle after voluntary contraction. In general practice, the most common cause of myotonia is the genetic disorder, myotonic dystrophy. Other inherited disorders (including the channelopathies) can also present with myotonia or periodic weakness. Mutations in genes encoding voltage-gated ion channels (sodium, chloride, calcium and potassium) cause inherited disorders of skeletal muscle excitability (eg myotonia congenita). A key feature of these disorders is that symptoms fluctuate, often influenced by environmental triggers (eg diet, temperature).

Refer patients for expert care.