Potassium Aggravated Myotonia

**Semantic type:** Disease or Syndrome

**Definition:** A group of autosomal dominant inherited non-dystrophic myotonias caused by mutations of the SCN4A gene, resulting in sodium muscle channelopathy. They are characterized by muscle stiffness, which worsens by ingestion of potassium-rich food. This group includes myotonia fluctuans, myotonia permanens, and acetazolamide-responsive myotonia.

**Synonyms:** - PAM