Previous studies had shown that rare inherited mutations could produce the disorder. Drug-induced LQTS is a common and equally dangerous condition whose widespread basis has been unclear. This new Yale study shows that a common gene variant that is not harmful by itself can create a risk for a lethal response to the medication. D., associate professor of pediatrics and cellular and molecular physiology, and chief of the Section of Developmental Biology and Biophysics at Yale School of Medicine .
Normal heartbeats are due to the orchestrated opening and closing of proteins called ion channels.
Ion channels act as pathways for ions across cell membranes. Potassium channels pass potassium ions and in the heart act to end each beat. The study shows that a variant of a potassium channel gene present in some people places them at risk for LQTS and lethal arrhythmia when they take the antibiotic trimethoprim-sulfamethoxazole. The variant is a change of a single DNA base in the KCNE2 gene. This SNP produces channels whose functions are blocked by normal blood levels of sulfamethoxazole.