Large Deletion in KCNQ1 Identified in a Family with Jervell and Lange-Nielsen Syndrome

Long QT syndrome (LQTS) is a genetically heterogeneous disorder associated with sequence variations in more than 10 genes; in some cases, it is caused by large deletions or duplications among the main, known LQTS-associated genes. Here, we describe a 14-month-old Korean boy with congenital hearing loss and prolonged QT interval whose condition was clinically diagnosed as Jervell and Lange-Nielsen syndrome (JLNS), a recessive form of LQTS. Genetic analyses using sequence analysis and multiplex ligation-dependent probe amplification (MLPA) assay revealed a large deletion spanning exons 7-10 as well as a frameshift mutation (c.1893dup; p.Arg632Glnfs*20). To our knowledge, this is the first report of a large deletion in KCNQ1 identified in JLNS patients. This case indicates that a method such as MLPA, which can identify large deletions or duplications needs to be considered in addition to sequence analysis to diagnose JLNS.

A Case of Congenital Long QT Syndrome Associated with Deafness and Syncope

Congenital long QT syndrome (LQTS) is an inherited disease characterized by prolonged QT intervals and polymorphic ventricular tachycardia. The clinical manifestations vary from sudden cardiac death by ventricular arrhythmia to asymptom throughout life. In 1957, Jervell and Lange-Nielsen reported a syndrome of congen-ital sensory deafness associated with a prolonged QT interval in four children. The affected children had multiple syncopal episodes, and three died suddenly. The mode of inheritance is autosomal recessive. Affected persons are susceptible to recurrent syncope, and they have a high incidence of sudden death and short life expectancy. We report a case and review the literature on long QT syndrome diagnosed in a 30-year-old female with a history of convulsion and loss of consciousness during delivery.