LQT10 is a sub-type of Romano-Ward syndrome, a variant of the familial long QT syndrome. It is characterized by a mutation (L179F) in the SCN4B gene (PMID:17592081). SCN4B is also associated with familial atrial fibrillation 17 (ATFB17) (PMID:23604097) or sudden infant death (PMID:20226894). This indicates that long QT syndrome may share a common genetic origin with familial atrial fibrillation as well as sudden infant death.
Medeiros-Domingo et al. (2007) reported a 5-year-old Mexican mestizo girl who at 21 months of age was found to have asymptomatic bradycardia with rates less than 60 bpm. An ECG revealed profound QT prolongation with a QTc of ... Medeiros-Domingo et al. (2007) reported a 5-year-old Mexican mestizo girl who at 21 months of age was found to have asymptomatic bradycardia with rates less than 60 bpm. An ECG revealed profound QT prolongation with a QTc of 712 ms and intermittent 2:1 AV block; during 1:1 conduction, macroscopic T-wave alternans was observed. The patient's medical history included fetal bradycardia noted at 24 weeks of gestation and a small ventricular septal defect that spontaneously closed by 6 months of age. She remained asymptomatic after placement of an epicardial pacemaker. She had 2 paternal great aunts who had sudden cardiac death, 1 at age 35 years after delivery of twins and 1 at age 8 years during exercise. Medeiros-Domingo et al. (2007) noted that the ECG features in the proband, with a long isoelectric ST segment, late-onset T wave, and 2:1 AV block, were similar to those seen in SCN5A (600163)-mediated LQT3 (603830).
In affected members of a 4-generation Mexican mestizo pedigree with long QT syndrome, Medeiros-Domingo et al. (2007) analyzed the 9 known LQTS-associated genes (see LQT1; 192500) but found no mutations. Analysis of the 4 genes encoding sodium channel ... In affected members of a 4-generation Mexican mestizo pedigree with long QT syndrome, Medeiros-Domingo et al. (2007) analyzed the 9 known LQTS-associated genes (see LQT1; 192500) but found no mutations. Analysis of the 4 genes encoding sodium channel beta subunits, SCN1B (600235), SCN2B (601327), SCN3B (608214), and SCN4B (608256), revealed heterozygosity for a missense mutation in SCN4B (608256.0001) that segregated with the phenotype in the pedigree with incomplete penetrance. The mutation was not found in 800 control alleles, 400 of which were ethnically matched.