The muscular dystrophies.

Duchenne muscular dystrophy, the most common childhood-onset muscular dystrophy, is X-linked and is associated with cardiac and mental abnormalities. Becker's muscular dystrophy is similar to but milder than Duchenne muscular dystrophy. The rare facioscapulohumeral muscular dystrophy has an autosomal dominant mode of transmission. Myotonic muscular dystrophy is the most common of the adult-onset muscular dystrophies. Treatable diseases that must be excluded include polymyositis, potassium disorders and endocrine abnormalities.