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References OMIM Gene GeneReviews HGMD HGNC
last update : 16-06-2009
Symbol LQT3
Location 3p22.2
Name long QT syndrome with ventricular tachyarrhythmia, type 3
Corresponding gene SCN5A
Main clinical features
  • characterized by syncopes, seizures, predisposing to torsades de pointes and ventricular fibrillation, potentially increasing the inward Na+ currents leading to a high level of membrane depolarization
  • also sudden infant death syndrome (frequency unknown, SIDS Omim: 272120)
  • associated in any cases with left ventricular noncompaction
  • Genetic determination autosomal dominant
    Function/system disorder cardiovascular
    Type disease
    Gene product
    Name sodium channel voltage-gated type V, alpha (SCN5A)
    Genotype/Phenotype correlations
  • non-sens mutation W1421X, leading to early death, in association with polymorphism R1193Q lead only to mild phenotype (R1193Q mutation has a complementary role in alleviating the deleterious effects conferred by W1421X in the function of the SCN5A )
  • at least five LQT3 mutations (S941N, A1330P, S1103Y, R1826H, and A997S) have been associated with SIDS (PMID: 19302788))
  • S1333Y channels showed the gain of Na+ channel function characteristic of LQT3, including a persistent inward Na+ current and is associated to SIDS (PMID: 19302788))