This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Potassium aggravated myotonia is a group of diseases that causes tensing and stiffness (myotonia) of skeletal muscles, which are the muscles used for movement. The three types of potassium-aggravated myotonia include myotonia fluctuans, myotonia permanens, and acetazolamide-sensitive myotonia. Potassium aggravated myotonia is different from other types of myotonia because symptoms get worse when an affected individual eats food that is rich in potassium. Symptoms usually develop during childhood and vary, ranging from infrequent mild episodes to long periods of severe disease. Potassium aggravated myotonia is an inherited condition that is caused by changes (mutations) in the SCN4A gene. Treatment begins with avoiding foods that contain large amounts of potassium; other treatments may include physical therapy (stretching or massages to help relax muscles) or certain medications (such as mexiletine, carbamazapine, or acetazolamide).
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