Glossary / Lexicon

Myotonia congenital refers to a nonprogressive muscle disorder that develops from infancy to childhood. Myotonia is characterized by stiff muscles that take a long time to relax after contraction. It is generally not painful. Unlike many other myopathies, the muscles that are affected (arms, legs, and face) enlarge and do not weaken. It is also known as Thomsen's disease.