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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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Your Question

I have hypokalemic periodic paralysis and plan on having children soon. Could my condition worsen during pregnancy and/or childbirth? Does this condition affect the development of a fetus?  How rare is this condition in African Americans?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

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

What are the symptoms of hypokalemic periodic paralysis?

Hypokalemic periodic paralysis involves attacks of muscle weakness or loss of muscle movement (paralysis) that come and go. The weakness or paralysis is most commonly located in the shoulders and hips, affecting the muscles of the arms and legs. Muscles of the eyes and those that help you breathe and swallow may also be affected. There is normal muscle strength between attacks.[3] 

Attacks usually begin in adolescence, but they can occur before age 10. How often the attacks occur varies. Some people have attacks every day, while others have them once a year. Episodes of muscle weakness usually last between a few hours and a day.[3]

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, alcohol, 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.[1][3]

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.[1]
Last updated: 9/16/2009

What causes hypokalemic periodic paralysis?

Hypokalemic periodic paralysis is caused by mutations in the CACNA1S and SCN4A genes. 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.[1]

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.[1]

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.[1]

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

Could my hypokalemic periodic paralysis worsen during pregnancy and/or childbirth?

Data regarding the management of hypokalemic periodic paralysis during pregnancy and delivery is limited.[11664][4] The information that is available indicates that pregnancy and delivery may exacerbate the condition.[5] This makes management of periodic paralysis during pregnancy and delivery a challenge.[6]

Studies indicate that potassium management should be no different from prior to pregnancy. Carbonic anhydrase inhibitors like acetazolamide and dichlorphenamide are FDA Pregnancy Category C. Their use must be weighed against the risk of not taking them. Many women choose to avoid carbonic anhydrase inhibitors for the duration of their pregnancy. For some, this is tolerable, for others, it is exceedingly challenging. Of note, eplerenone is FDA Pregnancy Category B and is the favored option for those patients who cannot manage on potassium supplementation alone.[6]

As far as delivery goes, vaginal delivery is usually possible with monitoring and epidural analgesia, avoiding active maternal expulsive efforts (passive descent of the fetus and elective outlet forceps) and other stimulating factors (carbohydrate loads (IV glucose), maternal stress, betamimetics, epinephrine). Administration of IV potassium supplementation is often necessary.[5][4] Concerns include that stress during delivery, labor pain, and expulsive efforts during the second stage of labor might combine to result in a paralytic episode. General anesthesia, postoperative stress, glucose-containing IV solutions, and long-acting neuromuscular blockers are also associated with postoperative paralytic episodes.[4] 

To access case studies of pregnancy in women with hypokalemic periodic paralysis, you can visit the following link from the Periodic Paralysis News Desk. 
http://www.hkpp.org/physicians/birth_hypokpp_2.html 

You can find other relevant journal articles on the effects of pregnancy and delivery on hypokalemic periodic paralysis through a service called PubMed, a searchable database of medical literature. Information on finding an article and its title, authors, and publishing details is listed here.  Some articles are available as a complete document, while information on other studies is available as a summary abstract.  To obtain the full article, contact a medical/university library (or your local library for interlibrary loan), or order it online using the following link. Using "hypokalemic periodic paralysis AND pregnancy" as your search term should locate articles. To narrow your search, click on the “Limits” tab under the search box and specify your criteria for locating more relevant articles.  Click here to view a search.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed

The National Library of Medicine (NLM) Web site has a page for locating libraries in your area that can provide direct access to these journals (print or online). The Web page also describes how you can get these articles through interlibrary loan and Loansome Doc (an NLM document-ordering service). You can access this page at the following link http://nnlm.gov/members/. You can also contact the NLM toll-free at 888-346-3656 to locate libraries in your area.

Last updated: 9/16/2009

Can hypokalemic periodic paralysis affect the development of a fetus?

Although we were not able to locate any reports describing widespread issues with fetal development in mothers with hypokalemic periodic paralysis, there may be concerns for the baby immediately following birth.

The medical team at delivery should be prepared to support a newborn who experiences an episode of flaccid paralysis within moments or hours of birth, and infants of affected mothers require close monitoring. Feeding and respiration appear to be the major concerns. Some of infants developed respiratory issues during their first moments or hours.[7]

Last updated: 9/16/2009

Is it appropriate to have my child tested for hypokalemic periodic paralysis?

When a disease-causing mutation is identified in an affected individual, testing of at-risk, asymptomatic family members is appropriate because of the risk of unexpected acute paralysis and/or malignant hyperthermia. When the results of presymptomatic testing are not known, the at-risk family members must be considered at risk for complications; and precautions must be taken, particularly in the administration of anesthesia.[2]

Prenatal diagnosis for pregnancies at increased risk is possible by analysis of DNA extracted from fetal cells obtained by amniocentesis usually performed at approximately 15-18 weeks' gestation or chorionic villus sampling (CVS) at approximately ten to 12 weeks' gestation. The disease-causing allele of an affected family member must be identified before prenatal testing can be performed.[2]

Requests for prenatal testing for conditions such as hypokalemic periodic paralysis that do not affect intellect and have some treatment available are not common. Although most centers would consider decisions about prenatal testing to be the choice of the parents, discussion of these issues is appropriate.[2]

The appropriate time for testing your child is a decision which chould be made with your doctor or a genetics professional. Genetics professionals are a source of information for individuals and families regarding genetic diagnosis, natural history, treatment, mode of inheritance, and genetic risks to other family members. To find a genetics clinic, we recommend that you contact your primary doctor for a referral. Click here to learn more about genetic consultations.

The following online resources can also help you find a genetics professional in your community:

  * GeneTests - A searchable directory of US and international genetics and prenatal diagnosis clinics. Go to the following link and click on 'Clinic Directory' to find a genetic service close to you.
http://www.geneclinics.org/

  * ResourceLink - A database of genetics counseling services, searchable by location, name, institution, type of practice, or specialty. Hosted by the National Society of Genetic Counselors.
http://www.nsgc.org/resourcelink.asp


 

Last updated: 9/16/2009

How rare is hypokalemic periodic paralysis in African Americans?

After an extensive search of the resources available to us, we have not been able to locate any specific statistical data regarding the prevalence of this condition in African Americans.
Last updated: 9/16/2009

References