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Disease Profile

Hyperkalemic periodic paralysis

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-9 / 1 000 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

HYPP; Gamstorp disease; Gamstorp episodic adynamy;


Congenital and Genetic Diseases; Nervous System Diseases


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]


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.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Cerebral palsy
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 ]

EMG abnormality
Episodic flaccid weakness
Periodic hyperkalemic paralysis
Reduced tendon reflexes
30%-79% of people have these symptoms
Muscle twitch
Gait disturbance
Abnormal gait
Abnormal walk
Impaired gait

[ more ]

Elevated serum potassium levels
Muscle ache
Muscle pain

[ more ]

5%-29% of people have these symptoms
Abnormal heart rate
Heart rhythm disorders
Irregular heart beat
Irregular heartbeat

[ more ]

Bowel incontinence
Loss of bowel control
Chest pain
Congestive heart failure
Cardiac failure
Cardiac failures
Heart failure

[ more ]

Death in early adulthood
Death in infancy
Infantile death
Lethal in infancy

[ more ]

Feeding difficulties in infancy
Flexion contracture
Flexed joint that cannot be straightened
Low blood potassium levels
Low blood sodium levels
Malignant hyperthermia
Muscle tissue disease
Weakness of muscles controlling eye movement
Pins and needles feeling

[ more ]

Respiratory insufficiency
Respiratory impairment
Skeletal muscle atrophy
Muscle degeneration
Muscle wasting

[ more ]

Skeletal muscle hypertrophy
Increased skeletal muscle cells
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
Infantile onset
Onset in first year of life
Onset in infancy

[ more ]



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.


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

      Organizations Providing General Support

        Learn more

        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

        • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
        • MedlinePlus Genetics contains information on Hyperkalemic periodic paralysis. This website is maintained by the National Library of Medicine.
        • 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.


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