Common cardiac sodium channel variant associated with sudden infant death in African Americans

Steve A.N. Goldstein and colleagues from the Pritzker School of Medicine in Chicago have found that a specific mutation, called S1103Y, in a heart protein known as SCN5A is associated with a dramatic, 24-fold increased risk of sudden infant death syndrome (SIDS) in African American infants.

The authors show that this mutant protein, when exposed to acidic conditions (which can be caused by low blood oxygen levels when infants are placed in the face-down or "prone" sleeping position), malfunctions in a way that has been previously shown to trigger an irregular heartbeat. The study, which appears in the February issue of the Journal of Clinical Investigation, suggests the existence of a genetic predisposition to SIDS and also demonstrates a relationship between genes and the environment in the development of this fatal syndrome.

In an accompanying commentary, Jonathan Makielski from the University of Wisconsin writes, "These findings provide an excellent illustration of a causal relationship between the interaction of the environment and genetic background in SIDS. For families of SIDS victims, a clear delineation of risk factors, both genetic and environmental, will be instrumental in identifying children who may benefit from therapeutic intervention."

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