Cardiac sodium channel gene mutations and sudden infant death syndrome: confirmation of proof of concept?

Sudden infant death syndrome (SIDS) is a multifactorial disorder in which newborns tragically die in their sleep for no obvious reason and without prior warning. SIDS is defined as “the sudden death of an infant which is unexpected by history, and in which a full postmortem examination fails to demonstrate an adequate cause of death.”1 Although SIDS may occur in more than one child in a family, it has not been generally considered an inherited problem. The cause of SIDS has been speculated to be a mechanical airway problem, such as smothering, aspiration, or positional effects; child abuse; inborn errors of metabolism; brain stem dysfunction; or medication-induced.2 For many years, Schwartz and Sergantini3 and others4,5 have suggested the possibility of arrhythmogenic factors, although this has met with significant resistance over the years.6 In 1998, Schwartz et al7 presented titillating data suggesting that a significant percentage of SIDS cases were associated with a prolonged QT interval on screening ECGs and noted the possibility that long-QT syndrome (LQTS), an inherited disorder, is a common cause of SIDS. These authors then provided further support for this hypothesis when they identified a mutation in the cardiac sodium channel gene SCN5A in a near-SIDS case.8 In the present issue of Circulation, Wedekind et al provide further support for this concept.9