This finding represents the first molecular evidence to unlock the mystery behind SIDS.
A team of investigators led by Michael J. Ackerman, M.D., Ph.D., from Mayo Clinic, the Arkansas State Crime Laboratory, Baylor College of Medicine and the University of Wisconsin, Madison, examined 93 cases of SIDS or possible SIDS. Tissue collected from these cases was examined for a specific defect within a gene in the heart, the SCN5A gene. The SCN5A gene encodes a cardiac sodium channel that acts as an electrical tunnel and controls the heart's rhythm. Two of the 93 cases possessed SCN5A mutations.
Although that statistic may seem low, it represents a key to preventing future infant deaths by considering lethal heart rhythm disturbances as a possible cause for some cases. Future research will build upon this finding to examine other potential causes of SIDS.
"There will certainly be multiple reasons for SIDS discovered in the future," says Dr. Ackerman, a Mayo Clinic pediatric cardiologist. "Until advances related to the Human Genome Project, proving a cardiac electrical defect in SIDS has been difficult because there are no clues left at autopsy. Through molecular genetic testing on deceased infants, this study, however, identifies a whole new class of genes which could be considered for SIDS."
Although the causes of SIDS may be many, most remain in the realm of theories. SIDS, defined as the sudden and unexpected death of an apparently healthy infant, remains elusive and devastating. Despite the efforts of nationwide campaigns recommending infants be placed on their backs during sleep, SIDS continues to be the leading cause of death in the first year of life. Nearly 3,000 infants in the United States will fail to reach their first birthday this year because of SIDS.
What is not yet established is how many SIDS cases can be traced back to cardiac gene mutations. However, if further research demonstrates that 5-10 percent of SIDS cases may be due to such defects, it may be possible in the future to identify such at-risk infants shortly after birth by special molecular genetic tests not currently available. Defects in the identified cardiac channel genes could lead to later risk of death by congenital long QT syndrome or Brugada syndrome in adolescence if a child escapes death by SIDS during infancy.
"This is step one of many that could eventually prevent SIDS," says Dr. Ackerman. "This study attempts to make SIDS less of a mysterious 'black box.' We're just starting to be able to identify those infants that may be at risk for SIDS and take steps to prevent the incidence of death."
Note: Copies of the study may be obtained from the Journal of the American Medical Association (JAMA) by visiting jama.ama-assn.org.
Dr. Ackerman will be available to respond to inquiries beginning Tuesday, Nov. 13, 2001.
Tuesday, Nov. 13, 2001
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