The Jervell and Lange-Nielsen syndrome (JLNS) is an autosomal recessive syndrome characterized by congenital deafness and cardiac phenotype (QT prolongation, ventricular arrhythmias, and sudden death). JLNS has been shown to occur due to homozygous mutation in KCNQ1 or KCNE1. There have been a few clinical case reports on JLNS in Korea; however, these were not confirmed by a genetic study. We identified compound heterozygous mutations in KCNQ1 in a 5-yr-old child with JLNS, who visited the hospital due to recurrent syncope and seizures and had congenital sensorineural deafness. His electrocardiogram revealed a markedly prolonged corrected QT interval with T wave alternans. The sequence analysis of the proband revealed the presence of novel compound heterozygous deletion/splicing error mutations (c.828-830 delCTC, p.S277del/c.921G>A, p.V307V). Each mutation in KCNQ1 was identified on the maternal and paternal side. With beta-blocker therapy the patient has remained symptom-free for three and a half years.
Asian Continental Ancestry Group/*genetics ; Child, Preschool ; Electrocardiography ; Exons ; Family ; Gene Deletion ; Heterozygote ; Humans ; Jervell-Lange Nielsen Syndrome/diagnosis/*genetics ; KCNQ1 Potassium Channel/*genetics ; Male ; Mutation ; Pedigree ; Republic of Korea

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.
Adolescent ; Alleles ; Base Sequence ; Electrocardiography ; Exons ; Frameshift Mutation ; Heterozygote ; Humans ; Jervell-Lange Nielsen Syndrome/diagnosis/*genetics ; KCNQ1 Potassium Channel/*genetics ; Male ; Nucleic Acid Amplification Techniques ; Pedigree ; Sequence Analysis, DNA ; Sequence Deletion