Myotonic dystrophy

**Definition:** Myotonic dystrophy is a group of inherited muscular disorders. It is the most common form of muscular dystrophy that begins in adulthood. Myotonic dystrophy is characterised by progressive muscle wasting and weakness, and prolonged muscle contractions (myotonia) that are not able to relax after use. Other signs and symptoms of myotonic dystrophy include slurred speech or temporary locking of their jaw, cataracts and cardiac conduction defects. In affected men, hormonal changes may lead to early balding and infertility. The clinical severity varies widely among affected patients, even among members of the same family.

**Exclusions:** - Myasthenia gravis or certain specified neuromuscular junction disorders - Secondary myopathies