Background: Long QT syndromes (LQTS) are inherited cardiac disorders caused by mutations in the genes that encode sodium or potassium transmembrane ion channel proteins. More than 200 mutations, in at least six genes, have been found in these patients. The Jervell and Lange-Nielsen (JLN) syndrome is the recessive form of the disease and is associated with deafness. Few families with JLN syndrome and genetic studies are reported in the literature.
Methods: The KCNQ1 (KvLQT1) gene in a Mexican family with Jervell-Lange-Nielsen long QT syndrome was analyzed using an automated sequence method.
Results: A missense mutation was found in the three affected individuals. This mutation is associated with complete loss of channel function. Correlation with the phenotype showed a prolonged QTc interval and deafness in the two siblings homozygous to the mutation. The mother, who was heterozygous for the mutation, also had prolonged QTc interval without deafness. The father and younger brother had normal QTc intervals. The mutation was not found in 50 healthy controls studied.
Conclusions: We describe for the first time a mutation in the KCNQ1 gene in a Mexican family with JLN long QT syndrome. This mutation produces an amino acid change (Gly-Arg) at protein level at the 168 residue. This mutation has been previously reported in Caucasian families with LQTS.