KCNE2 and familial long QT syndrome: More than 90% of the mutations are found in five of the genes (KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2), and mutation analysis of these five LQTS-causing genes reveals a mutation in about 75% of patients with a clinical diagnosis of LQTS[8,12-15].