Identical twins with long QT syndrome associated with a missense mutation in the S4 region of the HERG

Familial long QT syndrome (LQTS) is caused by mutations in genes encoding i on channels important in determining ventricular repolarization. Mutations in at least five genes have been associated with the LQTS. Fire genes, KCNQ 1, HERG, SCN5A, KCNE1, and KCNE2, have been identified. We have identified a missense mutation in the HERG gene in identical twins in a Japanese famil y with LQTS. The identical twins in our study had QT prolongation and the s ame missense mutation. However only the proband had a history of syncope. A lthough many mutations in LQT genes have been reported, there are few repor ts of twins with LQTS. This is the first report, to our knowledge, of ident ical twins with a HERG gene mutation.