Cardiac ion channel mutations in the sudden infant death syndrome

Sudden infant death syndrome (SIDS) is characterized by the sudden death of an infant that occurs during sleep and remains unexplained despite thorough examination. In addition to clinical associations such as prone sleeping and exposure to cigarette smoke, several genetic factors have been identified with regard to SIDS, including autonomic disorders, immunologic polymorphisms and metabolic disorders. In the past decade, postmortem genetic analysis ('molecular autopsy') of SIDS cases has revealed a number of cardiac ion channel mutations that are associated with arrhythmia syndromes, including the long QT syndrome, Brugada syndrome and short QT syndrome. Mutations have been found in genes encoding (subunits of) cardiac potassium, sodium and calcium channels, as well as in genes involved in the trafficking or regulation of these channels. Here, we review the literature on cardiac ion channel mutations in relation to SIDS. Combining data from population-based cohort studies, we conclude that at least one out of five SIDS victims carries a mutation in a cardiac ion channel-related gene and that the majority of these mutations are of a known malignant phenotype. Genetic analysis is therefore recommended in cases of sudden infant death. More research is required to further elucidate the pathophysiology of SIDS and to determine whether genetic or electrocardiographic screening of apparently healthy infants should be pursued.