ABSTRACT
Introduction: Long QT syndrome (LQTS), an inherited cardiac arrhythmia, is a disorder of ventricular repolarisation characterised by electrocardiographic abnormalities and the onset of torsades de pointes leading to syncope and sudden death. Genetic polymorphisms in 5 well-characterised cardiac ion channel genes have been identified to be responsible for the disorder. The aim of this study is to identify disease-causing mutations in these candidate genes in a LQTS family. Materials and Methods: The present study systematically screens the coding region of the LQTS-associated genes (KCNQ1, HERG, KCNE1, KCNE2 and SCN5A) for mutations using DNA sequencing analysis. Results: The mutational analysis revealed 7 synonymous and 2 non-synonymous polymorphisms in the 5 ion channel genes screened. Conclusion: We did not identify any clear identifiable genetic marker causative of LQTS, suggesting the existence of LQTS-associated genes awaiting discovery.
Long QT syndrome (LQTS), a form of life-threatening cardiac arrhythmia, is a rare but significant clinical disorder, with a prevalence of 1 in 10,000 to 15,000 individuals.1 LQTS is a disorder of ventricular repolarisation characterised by electrocardiographic abnormalities, predominantly a prolongation of the QT interval and ventricular tachyarrhythmia, particularly torsades de pointes leading to syncopes, seizures and sudden death.2 Congenital LQTS is an inherited heterogenous disorder caused by mutations at various loci, giving rise to a prolonged QT interval. There exists the more common autosomal dominant Romano-Ward syndrome (RW)3 and the less common autosomal recessive Jervell and Lange-Nielsen syndrome (JLN),4 the latter which is associated with sensorineural deafness.5
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