Chromosomal Testing Explores Causes of Sudden Infant Death Syndrome (SIDS)

As DNA sequencing costs come down, the researchers want to use whole-genome sequencing to investigate SIDS, a single test that could reduce the need for CMA.

Chromosomal microarray analysis (CMA) identifies the cause of sudden infant death syndrome (SIDS) or its counterpart in older kids, known as sudden unexplained death in childhood (SUDC).

The researchers, led by Richard Goldstein, MD, Ingrid Holm, MD, MPH, and Catherine Brownstein, MPH, PhD, call for making CMA routine in investigating SIDS and SUDC. They published their study findings online in the journal Advanced Genetics.

Sudden Infant Death Syndrome - Overview
Sudden Infant Death Syndrome is death of a baby, under one year of age that occurs in sleep and cannot be explained.

‘Chromosomal microarray analysis (CMA) is used routinely in children with conditions such as autism, developmental delay, and multiple congenital anomalies, and children with undiagnosed conditions.’

“We think we have enough information to say that CMA is worth considering when a child has died without explanation, and worth exploring further as a way to understand these deaths better,” says Goldstein, who directs Robert’s Program on Sudden Unexpected Death in Pediatrics at Boston Children’s and was a senior author on the study.

The Genetics of Sudden Infant Death Syndrome

The team used CMA to test samples from 116 deceased infants and toddlers up to 28 months old whose deaths were classified as SIDS or SUDC. In 14 children (12 percent), CMA identified deletions or duplications of segments of the child’s DNA or small DNA rearrangements that were pathogenic or “favoring pathogenic.”

To further validate their findings, the researchers compared CMA results in SIDS/SUDC patients with those in control groups of children from the community and two cohorts of children with an autism spectrum disorder. When scored for the likelihood of potentially impactful chromosomal changes on CMA, the SIDS/SUDC group scored significantly higher than controls, but had scores similar to those of children with autism spectrum disorder (ASD).

Many of the CMA findings had no obvious relationship to SIDS/SUDC and call for further investigation. For example, two children had undiagnosed Klinefelter syndrome, in which boys are born with an extra X chromosome but generally have a normal lifespan. Several identified chromosomal deletions/duplications have also been associated with neurodevelopmental conditions, including seizures, ASD, developmental delay, and schizophrenia.

Sudden Death in Children - Risk Factors, Symptoms, Diagnosis and Treatment
Sudden death in children occurs within one hour of the symptom onset and it is mostly due to the underlying cardiovascular pathology.

In previous work, Boston Children’s researchers used whole-exome sequencing (sequencing the 1 to 2 percent of the genome that encodes proteins) to evaluate children whose deaths were classified as SIDS or SUDC. In that study, 11 percent of children had genetic variants (alterations) that likely played a role in their deaths. It remains to be seen to what extent CMA would add to these findings and how much overlap there is between the genes found to be altered on exome sequencing and the genes affected by DNA deletions/duplications.

The team hopes their findings will encourage medical examiners investigating SIDS deaths to reach out to them for assistance.

Smoking, Drinking Combined can Contribute to Higher Risk for SIDS
Smoking and drinking while pregnant can significantly raise the risk for sudden infant death syndrome (SIDS), according to a new study.

“Medical examiners are interested in genetic investigations, but they lack the resources, especially when it comes to interpreting the results,” says Goldstein. “We’re trying to move that ball forward and provide useful information.”

Adding to exome sequencing and chromosomal abnormalities on CMA, the researchers recently got a grant from the American SIDS Institute to study more complex structural changes in chromosomes that might contribute to SIDS and SUDC, using an advanced genomics platform called the Bionano Saphyr to image extremely long strands of DNA.

Smoking and Drinking During Early Pregnancy Raise SIDS Risk
NIH-funded Safe Passage Study provides a look at how SIDS risk is influenced by the timing and amount of prenatal exposure to tobacco and alcohol.

“This technique gives us the ability to find structural variations that are too big for traditional DNA sequencing to pick up but too small for chromosomal microarray to detect,” says Brownstein, the study’s first author and scientific director of the Manton Center for Orphan Disease Research Gene Discovery Core at Boston Children’s. “We can also pick up instances when a segment of DNA ‘flips’ to a different location on the chromosome.”

The study was funded by the Robert’s Program on Sudden Unexplained Death in Pediatrics, the Jude Zayac Foundation, the National Institute of Child Health and Human Development (K23HD102589, R01 HD 090064, R01 HD 020991, P50HD105351), and the National Institute of Mental Health (U01 MH119690). The authors declare no conflicts of interest.

Source-Eurekalert