National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Hyperkalemic periodic paralysis


Other Names:
HYPP; Gamstorp disease; Gamstorp episodic adynamy; HYPP; Gamstorp disease; Gamstorp episodic adynamy; Adynamia episodica hereditaria with or without myotonia; Sodium channel muscle disease See More
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Hyperkalemic periodic paralysis is a genetic disease that causes episodes of extreme muscle weakness and an increase of the potassium levels in the blood. Muscle weakness during an attack usually affects the arms and legs and muscles of the eyes, throat, and trunk. Most often, these episodes involve a temporary inability to move muscles in the arms and legs. Episodes usually begin before age 20, usually between infancy and age 10. Normally an episode lasts for 15 minutes to an hour, but in some people the episodes may last a few days to a week. Episodes tend to increase in frequency until about age 50, after which they may occur less frequently. Factors that can trigger attacks include rest after strenuous exercise, potassium-rich foods, stress, fatigue, and exposure to cold. Depolarizing anesthetics should also be avoided. Muscle strength usually returns to normal between episodes, although many people continue to experience mild stiffness, particularly in muscles of the face and hands. Studies suggest more than 80% of people with hyperkalemic periodic paralysis over age 40 have permanent muscle weakness, most often affecting the leg muscles. About one third may develop a chronic progressive myopathy.[1] 

Hyperkalemic periodic paralysis is caused by mutations in the SCN4A gene and is inherited in an autosomal dominant manner. Diagnosis is based on clinical symptoms including the increase of blood potassium level during an episode, but normal levels of blood potassium level in between episodes. Genetic testing can confirm the diagnosis. Treatment is focused on avoiding triggers and decreasing the severity of an episode. At the first sign of muscle weakness, episodes in many people may be prevented or stopped by mild exercise and/or eating carbohydrates, inhalation of salbutamol, or intravenous calcium gluconate.[1]
Last updated: 8/18/2017

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Cerebral palsy 0100021
Elevated serum creatine kinase
Elevated blood creatine phosphokinase
Elevated circulating creatine phosphokinase
Elevated creatine kinase
Elevated serum CPK
Elevated serum creatine phosphokinase
High serum creatine kinase
Increased CPK
Increased creatine kinase
Increased creatine phosphokinase
Increased serum CK
Increased serum creatine kinase
Increased serum creatine phosphokinase
[ more ] 		0003236
EMG abnormality 0003457
Episodic flaccid weakness 0003752
Periodic hyperkalemic paralysis 0007215
Reduced tendon reflexes 0001315
30%-79% of people have these symptoms
Fasciculations
Muscle twitch
0002380
Gait disturbance
Abnormal gait
Abnormal walk
Impaired gait
[ more ] 		0001288
Hyperkalemia
Elevated serum potassium levels
0002153
Myalgia
Muscle ache
Muscle pain
[ more ] 		0003326
Myotonia 0002486
5%-29% of people have these symptoms
Arrhythmia
Abnormal heart rate
Heart rhythm disorders
Irregular heart beat
Irregular heartbeat
[ more ] 		0011675
Bowel incontinence
Loss of bowel control
0002607
Chest pain 0100749
Congestive heart failure
Cardiac failure
Cardiac failures
Heart failure
[ more ] 		0001635
Death in early adulthood 0100613
Death in infancy
Infantile death
Lethal in infancy
[ more ] 		0001522
Feeding difficulties in infancy 0008872
Flexion contracture
Flexed joint that cannot be straightened
0001371
Hypertonia 0001276
Hypokalemia
Low blood potassium levels
0002900
Hyponatremia
Low blood sodium levels
0002902
Malignant hyperthermia 0002047
Myopathy
Muscle tissue disease
0003198
Ophthalmoparesis
Weakness of muscles controlling eye movement
0000597
Paresthesia
Pins and needles feeling
Tingling
[ more ] 		0003401
Respiratory insufficiency
Respiratory impairment
0002093
Skeletal muscle atrophy
Muscle degeneration
Muscle wasting
[ more ] 		0003202
Skeletal muscle hypertrophy
Increased skeletal muscle cells
0003712
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance 0000006
Infantile onset
Onset in first year of life
Onset in infancy
[ more ] 		0003593
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Last updated: 7/1/2020

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
Differential diagnoses include secondary hyperPP caused by renal or endocrine diseases, other familial periodic paralyses such as hypokalemic or normokalemic PP (see these terms) and non dystrophic myotonias such as paramyotonia congenita (see this term).
Visit the Orphanet disease page for more information.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Hyperkalemic periodic paralysis. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Social Networking Websites

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Hyperkalemic periodic paralysis. This website is maintained by the National Library of Medicine.
  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • The National Institute of Neurological Disorders and Stroke (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Hyperkalemic periodic paralysis. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Weber F, Jurkat-Rott K, Lehmann-Horn F. Hyperkalemic Periodic Paralysis. GeneReviews. January 28 2016; https://www.ncbi.nlm.nih.gov/books/NBK1496/.