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Genetics Home Reference: your guide to understanding genetic conditions
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Hypokalemic periodic paralysis

Reviewed April 2007

What is hypokalemic periodic paralysis?

Hypokalemic periodic paralysis is a condition that causes episodes of extreme muscle weakness typically beginning in childhood or adolescence. Most often, these episodes involve a temporary inability to move muscles in the arms and legs. Attacks cause severe weakness or paralysis that usually lasts from hours to days. Some people may have episodes almost every day, while others experience them weekly, monthly, or only rarely. Attacks can occur without warning or can be triggered by factors such as rest after exercise, a viral illness, or certain medications. Often, a large, carbohydrate-rich meal or vigorous exercise in the evening can trigger an attack upon waking the following morning. Although affected individuals usually regain their muscle strength between attacks, repeated episodes can lead to persistent muscle weakness later in life.

People with hypokalemic periodic paralysis have reduced levels of potassium in their blood (hypokalemia) during episodes of muscle weakness. Researchers are investigating how low potassium levels may be related to the muscle abnormalities in this condition.

How common is hypokalemic periodic paralysis?

Although its exact prevalence is unknown, hypokalemic periodic paralysis is estimated to affect 1 in 100,000 people. Men tend to experience symptoms of this condition more often than women.

What genes are related to hypokalemic periodic paralysis?

Mutations in the CACNA1S and SCN4A genes cause hypokalemic periodic paralysis.

The CACNA1S and SCN4A genes provide instructions for making proteins that play 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) into muscle cells. The CACNA1S and SCN4A proteins form channels that control the flow of these ions. The channel formed by the CACNA1S protein transports calcium ions into cells, while the channel formed by the SCN4A protein transports sodium ions.

Mutations in the CACNA1S or SCN4A gene alter the usual structure and function of calcium or sodium channels. The altered channels cannot properly regulate the flow of 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 severe muscle weakness or paralysis.

A small percentage of people with the characteristic features of hypokalemic periodic paralysis do not have identified mutations in the CACNA1S or SCN4A gene. In these cases, the cause of the condition is unknown.

Related Gene(s)

Changes in these genes are associated with hypokalemic periodic paralysis.

  • CACNA1S
  • SCN4A

How do people inherit hypokalemic 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.

Where can I find information about diagnosis or management of hypokalemic periodic paralysis?

These resources address the diagnosis or management of hypokalemic periodic paralysis and may include treatment providers.

  • Gene Review: Hypokalemic Periodic Paralysis (http://www.ncbi.nlm.nih.gov/books/NBK1338)
  • Genetic Testing Registry: Hypokalemic periodic paralysis (http://www.ncbi.nlm.nih.gov/gtr/conditions/C0238358)
  • Genetic Testing Registry: Hypokalemic periodic paralysis 1 (http://www.ncbi.nlm.nih.gov/gtr/conditions/CN031165)
  • MedlinePlus Encyclopedia: Hypokalemic periodic paralysis (http://www.nlm.nih.gov/medlineplus/ency/article/000312.htm)

You might also find information on the diagnosis or management of hypokalemic periodic paralysis in Educational resources (http://www.ghr.nlm.nih.gov/condition/hypokalemic-periodic-paralysis/show/Educational+resources) and Patient support (http://www.ghr.nlm.nih.gov/condition/hypokalemic-periodic-paralysis/show/Patient+support).

General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook. Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).

To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

Where can I find additional information about hypokalemic periodic paralysis?

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

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

What other names do people use for hypokalemic periodic paralysis?

  • Familial Hypokalemic Periodic Paralysis
  • HOKPP
  • HypoKPP
  • HypoPP
  • Primary Hypokalemic Periodic Paralysis
  • Westphall disease

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide) and How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

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

Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).

What glossary definitions help with understanding hypokalemic periodic paralysis?

autosomal ; autosomal dominant ; calcium ; carbohydrate ; cell ; channel ; contraction ; familial ; gene ; hypokalemia ; inherited ; ions ; ion transport ; muscle cells ; potassium ; prevalence ; protein ; sodium

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).

References

  • Cannon SC. An expanding view for the molecular basis of familial periodic paralysis. Neuromuscul Disord. 2002 Aug;12(6):533-43. Review. (http://www.ncbi.nlm.nih.gov/pubmed/12117476?dopt=Abstract)
  • Fouad G, Dalakas M, Servidei S, Mendell JR, Van den Bergh P, Angelini C, Alderson K, Griggs RC, Tawil R, Gregg R, Hogan K, Powers PA, Weinberg N, Malonee W, Ptácek LJ. Genotype-phenotype correlations of DHP receptor alpha 1-subunit gene mutations causing hypokalemic periodic paralysis. Neuromuscul Disord. 1997 Jan;7(1):33-8. (http://www.ncbi.nlm.nih.gov/pubmed/9132138?dopt=Abstract)
  • Gene Review: Hypokalemic Periodic Paralysis (http://www.ncbi.nlm.nih.gov/books/NBK1338)
  • 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. Review. (http://www.ncbi.nlm.nih.gov/pubmed/17139526?dopt=Abstract)
  • Lehmann-Horn F, Jurkat-Rott K, Rüdel R. Periodic paralysis: understanding channelopathies. Curr Neurol Neurosci Rep. 2002 Jan;2(1):61-9. Review. (http://www.ncbi.nlm.nih.gov/pubmed/11898585?dopt=Abstract)
  • 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, Ptácek LJ. Correlating phenotype and genotype in the periodic paralyses. Neurology. 2004 Nov 9;63(9):1647-55. (http://www.ncbi.nlm.nih.gov/pubmed/15534250?dopt=Abstract)
  • 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. (http://www.ncbi.nlm.nih.gov/pubmed/16195244?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: April 2007
Published: November 24, 2014