Hyperkalemic periodic paralysis

Hyperkalemic periodic paralysis is a condition that causes episodes of extreme muscle weakness, usually beginning in infancy or early childhood. Most often, these episodes involve a temporary inability to move muscles in the arms and legs. Episodes tend to increase in frequency until about age 25, after which they may occur less frequently. Factors that can trigger attacks include rest after exercise, potassium-rich foods, stress, fatigue, and periods without food (fasting). Muscle strength improves between attacks, although many affected people continue to experience mild stiffness (myotonia), particularly in muscles of the face and hands.

Some people with hyperkalemic periodic paralysis have increased levels of potassium in their blood (hyperkalemia) during attacks. In other cases, attacks are associated with normal blood potassium levels (normokalemia). Ingesting potassium can trigger attacks in affected individuals, even if blood potassium levels do not go up.

How common is hyperkalemic periodic paralysis?

Hyperkalemic periodic paralysis affects an estimated 1 in 200,000 people.

What genes are related to hyperkalemic periodic paralysis?

Mutations in the SCN4A gene cause hyperkalemic periodic paralysis.

The SCN4A gene provides instructions for making a protein that plays an essential role in muscles used for movement (skeletal muscles). For the body to move normally, these muscles must tense (contract) and relax in a coordinated way. Muscle contractions are triggered by the flow of certain positively charged atoms (ions), including sodium, into muscle cells. The SCN4A protein forms channels that control the flow of sodium ions into these cells.

Mutations in the SCN4A gene alter the usual structure and function of sodium channels. The altered channels cannot properly regulate the flow of sodium ions into muscle cells, which reduces the ability of skeletal muscles to contract. Because muscle contraction is needed for movement, a disruption in normal ion transport leads to episodes of muscle weakness or paralysis.

Read more about the SCN4A gene.

How do people inherit hyperkalemic periodic paralysis?

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In most cases, an affected person has one parent with the condition.

What other names do people use for hyperkalemic periodic paralysis?

• Adynamia Episodica Hereditaria
• Familial Hyperkalemic Periodic Paralysis
• Gamstorp disease
• Gamstorp episodic adynamy
• HyperKPP
• HyperPP
• Primary Hyperkalemic Periodic Paralysis

Where can I find information about treatment for hyperkalemic periodic paralysis?

These resources address the management of hyperkalemic periodic paralysis and may include treatment providers.

• Gene Review: Hyperkalemic Periodic Paralysis Type 1
• MedlinePlus Encyclopedia: Hyperkalemic periodic paralysis

You might also find information on treatment of hyperkalemic periodic paralysis in Educational resources and Patient support.

Where can I find additional information about hyperkalemic periodic paralysis?

You may find the following resources about hyperkalemic periodic paralysis helpful. These materials are written for the general public.

• MedlinePlus - Health information (3 links)
• Additional NIH Resources - National Institutes of Health
• National Institute of Neurological Disorders and Stroke
• Educational resources - Information pages (5 links)
• Patient support - For patients and families (2 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Gene Tests - DNA tests ordered by healthcare professionals
• PubMed - Recent literature
• Online Books - Medical and science texts
• Scriver's Online Metabolic and Molecular Bases of Inherited Disease (OMMBID): Channelopathies: Episodic Disorders of the Nervous System
• OMIM - Genetic disorder catalog

See How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about hyperkalemic periodic paralysis?

• See How can I find a genetics professional in my area? in the Handbook.
• Ask the Genetic and Rare Diseases Information Center.
• Submit your question to Ask the Geneticist.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding hyperkalemic periodic paralysis?

atom ; autosomal ; autosomal dominant ; cell ; channel ; contraction ; familial ; fasting ; gene ; hyperkalemia ; ions ; ion transport ; mutation ; myotonia ; potassium ; protein ; skeletal muscle ; sodium ; sodium channel ; stress

References

• Bradley, W G((Walter George)); Neurology in clinical practice; 4th ed.; Philadelphia, PA : Butterworth-Heinemann, c2004. p1852-1853.
• Cannon SC. An expanding view for the molecular basis of familial periodic paralysis. Neuromuscul Disord. 2002 Aug;12(6):533-43. Review. PubMed citation
• Gene Review: Hyperkalemic Periodic Paralysis Type 1
• Jurkat-Rott K, Lehmann-Horn F. Paroxysmal muscle weakness - the familial periodic paralyses. J Neurol. 2006 Nov;253(11):1391-8. Epub 2006 Nov 30. PubMed citation
• Lehmann-Horn F, Jurkat-Rott K, Rudel R. Periodic paralysis: understanding channelopathies. Curr Neurol Neurosci Rep. 2002 Jan;2(1):61-9. Review. PubMed citation
• Miller TM, Dias da Silva MR, Miller HA, Kwiecinski H, Mendell JR, Tawil R, McManis P, Griggs RC, Angelini C, Servidei S, Petajan J, Dalakas MC, Ranum LP, Fu YH, Ptacek LJ. Correlating phenotype and genotype in the periodic paralyses. Neurology. 2004 Nov 9;63(9):1647-55. PubMed citation
• Venance SL, Cannon SC, Fialho D, Fontaine B, Hanna MG, Ptacek LJ, Tristani-Firouzi M, Tawil R, Griggs RC; CINCH investigators. The primary periodic paralyses: diagnosis, pathogenesis and treatment. Brain. 2006 Jan;129(Pt 1):8-17. Epub 2005 Sep 29. Review. PubMed citation