Overrepresentation of the proarrhythmic, sudden death predisposing sodium channel polymorphism S1103Y in a population-based cohort of African-American sudden infant death syndrome

Background: The S1103Y-SCN5A polymorphism has been implicated as a proarrhythmic, sudden death predisposing risk factor in African Americans, including one postmortem investigation of African-American infants with sudden infant death syndrome (SIDS). Objective: The purpose of this study was to assess whether the relatively African-American-specific common polymorphism S1103Y in the SCN5A-encoded cardiac sodium channel is overrepresented in SIDS among African Americans. Methods: Seventy-one cases from a population-based cohort of unexplained infant deaths among African Americans (37 females and 34 males, average age 3 ± 2 months, age range birth to 11 months) were submitted to the Mayo Clinic Windland Smith Rice Sudden Death Genomics Laboratory for postmortem genetic testing. Polymerase chain reaction and a restriction digest assay were performed to genotype this cohort for S1103Y. Results: Targeted mutational analysis of exon 18 in SCN5A of the African-American SIDS cohort (n = 71) revealed the S1103Y polymorphism in 16 (22.5%) of 71 African-American cases of SIDS compared to 135 (11.6%) of 1,161 ostensibly healthy adult African Americans (P = .01). Conclusion: This study provides an independent assessment of the prevalence of S1103Y-SCN5A among African-American infants with sudden, unexpected, unexplained death prior to their first birthday. Further scrutiny and quantification of the risk apparently associated with S1103Y appear warranted.