Rare Rheumatology News

Disease Profile

Long QT syndrome

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.


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



Long QT syndrome is a disorder of the heart’s electrical activity that can cause sudden, uncontrollable, and irregular heartbeats (arrhythmia), which may lead to sudden death. Long QT syndrome can be detected by electrocardiogram (EKG). It can be caused by a variety of different gene mutations (changes). It can also be acquired (noninherited) and may be brought on by certain medicines and other medical conditions.[1]


Signs and symptoms of the arrhythmias experienced by people with long QT syndrome includes unexplained fainting, seizures, drowning or near drowning, and sudden cardiac arrest or death.[1] You can read more about these and other symptoms of long QT syndrome on the National Heart Lung and Blood Institute's Web site by clicking here.

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
Abnormal heart rate
Heart rhythm disorders
Irregular heart beat
Irregular heartbeat

[ more ]

Sensorineural hearing impairment
30%-79% of people have these symptoms
Atrioventricular block
Interruption of electrical communication between upper and lower chambers of heart
5%-29% of people have these symptoms
Abdominal situs inversus
Low number of red blood cells or hemoglobin


Acquired long QT syndrome can be caused by certain medicines and medical conditions. Some medications that cause long QT syndrome include antihistamines and decongestants, antibiotics, antidepressants, and cholesterol-lowering medicines. Examples of medical conditions that can cause long QT syndrome include excessive diarrhea or vomiting and certain thyroid disorders.[1]

Inherited forms of long QT syndrome are caused by changes in genes that control the heart muscle’s electrical activity.[1] Inherited long QT syndrome may be isolated (occur alone without other associated symptoms) or be due to a genetic syndrome, such as Romano-Ward syndromeJervell Lang-Nielsen syndrome, Anderson-Tawil syndrome, and Timothy syndrome.[2]


Long QT syndrome is diagnosed on the basis of electrocardiographic (EKG) findings, clinical findings such as congenital deafness or unexplained fainting, and family history of long QT syndrome or sudden cardiac death. Genetic testing is often performed in families in whom the diagnosis of long QT syndrome has been made or is suspected on clinical grounds.

Testing Resources

  • Orphanet lists international laboratories offering diagnostic testing for this condition.


    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

      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

      • The KidsHealth Web site developed by the Nemours Foundation has an information page on arrhythmias. Click on KidsHealth to view the information page.
      • The Mayo Clinic has developed an information page on long QT syndrome. Click on the Mayo Clinic to view the information page.
      • The National Heart, Lung, and Blood Institute (NHLBI) has information on this topic. NHLBI is part of the National Institutes of Health and supports research, training, and education for the prevention and treatment of heart, lung, and blood diseases.

        In-Depth Information

        • The Merck Manuals offers a detailed review article on Long QT syndrome. Click on Merck Manuals to view the article.
        • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
        • MeSH® (Medical Subject Headings) is a terminology tool used by the National Library of Medicine. Click on the link to view information on this topic.
        • Online Mendelian Inheritance in Man (OMIM) lists the subtypes and associated genes for Long QT syndrome in a table called Phenotypic Series. Each entry in OMIM includes 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.



            1. Long QT syndrome. National Heart Lung and Blood Institute. 2007; https://www.nhlbi.nih.gov/health/dci/Diseases/qt/qt_all.html. Accessed 12/17/2008.
            2. Sovari AA, Kocheril AG, Assadi R Baas AS, Zareba W, Rosero S. Long QT syndrome. eMedicine. 2010; https://emedicine.medscape.com/article/157826-overview . Accessed 4/15/2011.

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