Recently, Wang et al¹ reported R1193Q mutation of SCN5A in one of the seven patients with acquired long QT syndrome (LQTS) and suggested that R1193Q is a functional mutation that can increase the susceptibility to this syndrome. The mutation destabilised channel inactivation and generated a persistent late current. The investigators found that 0.2% (4/2087) of the control subjects (of whom more than 90% were white and only 0.4% were Asian) also carried the mutation, and they suggested that it may be a risk factor for LQTS in the general population. The same mutation (listed as R1192Q using SCN5A RefSeq: NM_000335) has been reported in a Japanese infant with Brugada syndrome with frequent episodes of ventricular fibrillation.² They found that none of the 100 control subjects of Asian descent carried the variant.

We have identified the same R1193Q mutation by direct DNA sequencing of SCN5A in a four generation family of Chinese descent with cardiac conduction …