Myotonia Fluctuans

**Semantic type:** Disease or Syndrome

**Definition:** An autosomal dominant inherited potassium aggravated myotonia caused by mutations of the SCN4A gene. It is characterized by mild muscle stiffness that develops during rest approximately an hour after exercise and lasts for about an hour. It worsens by ingestion of potassium-rich food.

**Synonyms:** - Exercise-Induced Delayed-Onset Myotonia - MF