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Long QT syndrome 12(LQT12)

MedGen UID:
Concept ID:
Disease or Syndrome
Synonyms: LQT12
Modes of inheritance:
Autosomal dominant inheritance
MedGen UID:
Concept ID:
Intellectual Product
Sources: HPO, OMIM, Orphanet
Autosomal dominant inheritance refers to genetic conditions that occur when a mutation is present in one copy of a given gene (i.e., the person is heterozygous).
Autosomal dominant inheritance (HPO, OMIM, Orphanet)
Gene (location): SNTA1 (20q11.21)
OMIM®: 612955

Disease characteristics

Excerpted from the GeneReview: Long QT Syndrome
Long QT syndrome (LQTS) is a cardiac electrophysiologic disorder, characterized by QT prolongation and T-wave abnormalities on the ECG and the ventricular tachycardia torsade de pointes (TdP). TdP is usually self-terminating, thus causing a syncopal event, the most common symptom in individuals with LQTS. Syncope typically occurs during exercise and high emotions, less frequently at rest or during sleep, and usually without warning. In some instances, TdP degenerates to ventricular fibrillation and causes aborted cardiac arrest (if the individual is defibrillated) or sudden death. Approximately 50% of individuals with a pathogenic variant in one of the genes associated with LQTS have symptoms, usually one to a few syncopal spells. While cardiac events may occur from infancy through middle age, they are most common from the pre-teen years through the 20s. Some types of LQTS are associated with a phenotype extending beyond cardiac arrhythmia. In addition to the prolonged QT interval, associations include muscle weakness and facial dysmorphism in Andersen-Tawil syndrome (LQTS type 7), hand/foot, facial, and neurodevelopmental features in Timothy syndrome (LQTS type 8) and profound sensorineural hearing loss in Jervell and Lange-Nielson syndrome. [from GeneReviews]
Mariëlle Alders  |  Imke Christiaans   view full author information

Additional description

Congenital long QT syndrome (LQTS) is electrocardiographically characterized by a prolonged QT interval and polymorphic ventricular arrhythmias (torsade de pointes). These cardiac arrhythmias may result in recurrent syncope, seizure, or sudden death (Jongbloed et al., 1999). For a discussion of genetic heterogeneity of long QT syndrome, see LQT1 (192500).

Clinical features

MedGen UID:
Concept ID:
Sign or Symptom
Fainting is a temporary loss of consciousness. If you're about to faint, you'll feel dizzy, lightheaded, or nauseous. Your field of vision may white out or black out. Your skin may be cold and clammy. You lose muscle control at the same time, and may fall down. Fainting usually happens when your blood pressure drops suddenly, causing a decrease in blood flow to your brain. It is more common in older people. Some causes of fainting include. -Heat or dehydration . -Emotional distress . -Standing up too quickly . -Certain medicines . -Drop in blood sugar . -Heart problems . When someone faints, make sure that the airway is clear and check for breathing. The person should stay lying down for 10-15 minutes. Most people recover completely. Fainting is usually nothing to worry about, but it can sometimes be a sign of a serious problem. If you faint, it's important to see your health care provider and find out why it happened. .
Prolonged QTc interval
MedGen UID:
Concept ID:
Pathologic Function

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