SCN4A and sudden infant death syndrome: Alterations in sodium channel function in SIDS are qualitatively similar to those reported in infants with life-threatening respiratory events.9, 12, 14 Both gain-of-function and loss-of-function SCN4A variants can cause severe respiratory presentations in infancy and some of these cases have had a fatal outcome.8, 9, 14 In our study, only the SCN4A variants present in white SIDS cases caused significant alterations in channel function compared with wild type.