SCN5A and familial long QT syndrome: Apart from a number of common and rare polymorphisms, the results of screening for mutations in the LQTS genes KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2, associated with the LQTS types 1–3, 5, and 6, respectively, were limited to a single missense mutation in KCNQ1 (H105L).