Congenital long QT syndrome with compound mutations in the KCNH2 gene.
Congenital long QT syndrome is a genetic disorder encompassing a family of mutations that can lead to aberrant ventricular electrical activity. We report on two brothers with long QT syndrome caused by compound mutations in the KCNH2 gene inherited from parents who had no prolonged QT interval on electrocardiography. The proband had syncope, and his elder brother suffered from ventricular fibrillation. Genetic testing revealed that both brothers had multiple mutations in the KCNH2 gene, including a missense mutation of C1474T (exon 6) as well as a frameshift/nonsense mutation, resulting from the insertion of 25 nucleotides, which caused an altered amino acid sequence beginning at codon 302 and a premature termination codon (i.e., TAG) at codon 339 (exon 4). Family genetic screening found that their father had the same frameshift mutation, and their mother and sister had the same missense mutation, in the KCNH2 gene. However, these other family members were asymptomatic, with normal QT intervals on electrocardiography. These results suggest that compound mutations in the KCNH2 gene inherited independently from the parents made the phenotypes of their sons more severe.
Department of Cardiovascular Medicine, Institute of Health Biosciences, The University of Tokushima Graduate School, 2-50-1 Kuramoto, Tokushima, 770-8503, Japan.
Sachiko
S
Bando
Takeshi
T
Soeki
Tomomi
T
Matsuura
Toshiyuki
T
Niki
Takayuki
T
Ise
Koji
K
Yamaguchi
Yoshio
Y
Taketani
Takashi
T
Iwase
Hirotsugu
H
Yamada
Tetsuzo
T
Wakatsuki
Masashi
M
Akaike
Takeshi
T
Aiba
Wataru
W
Shimizu
Masataka
M
Sata
D004252:DNA Mutational Analysis; D000072237:ERG1 Potassium Channel; D004562:Electrocardiography; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics*; D016368:Frameshift Mutation; D020022:Genetic Predisposition to Disease; D040941:Heredity; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D012720:Severity of Illness Index; D055815:Young Adult
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human