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Genetic and Rare Diseases Information Center (GARD)

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Hypokalemic periodic paralysis


Other Names for this Disease
  • HOKPP
  • HypoPP
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Overview



What is hypokalemic periodic paralysis?

How is hypokalemic periodic paralysis inherited?

How is hypokalemic periodic paralysis diagnosed?


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. The duration and frequency of the episodes may vary. Hypokalemic periodic paralysis is caused by mutations in the CACNA1S and SCN4A genes which are inherited in an autosomal dominant fashion. A small percentage of people with the characteristic features of hypokalemic periodic paralysis do not have identified mutations in these genes. In these cases, the cause of the condition is unknown.[1] Paralytic crises can be treated with oral or IV potassium. Other management includes prevention of crises and support of specific symptoms.[2]
Last updated: 9/16/2009

How is hypokalemic periodic paralysis inherited?

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.[1]
Last updated: 4/20/2010

How is hypokalemic periodic paralysis diagnosed?

The diagnosis of hypokalemic periodic paralysis is based on a history of episodes of paralysis and low levels of potassium in the blood during attacks (less than 0.9 to 3.0 mmol/L), but not between attacks. An important part of the diagnosis is to rule out other potential causes, including myotonia, hyperthyroidism, and arrhythmia. Affected individuals typically have a family history consistent with autosomal dominant inheritance.[2]

Genetic testing is available for hypokalemic periodic paralysis. Of all individuals meeting diagnostic criteria for this condition, approximately 55 to 70 percent have mutations in the CACNA1S gene, and approximately 8 to 10 percent have mutations in the SCN4A gene. GeneTests lists the names of laboratories that perform clinical genetic testing of the CACNA1S and SCN4A genes for hypokalemic periodic paralysis. When a disease-causing mutation is identified in an affected individual, genetic testing can be performed for at-risk, asymptomatic family members.

Please note:  Most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.  See below for a list of online resources that can assist you in locating a genetics professional near you.
Last updated: 4/20/2010

References
  1. Hypokalemic periodic paralysis. Genetics Home Reference. April 2007; http://ghr.nlm.nih.gov/condition=hypokalemicperiodicparalysis. Accessed 4/20/2010.
  2. Sternberg D, Tabti N, Hainque B, Fontaine B. Hypokalemic periodic paralysis. GeneReviews. April 28, 2009; http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=hpp. Accessed 4/20/2010.