Rare genetic mutation linked to sudden infant death syndrome

March 29 (UPI) — Researchers have identified a potential genetic link for some cases of sudden infant death syndrome, the often unexpected and unexplained death of healthy children under 1.

In a study of infants in the United States and Britain, scientists found that genetic mutations associated with breathing muscles’ impairment are more frequent in children who have died from SIDS than in healthy babies.

The research, which was co-authored by scientists with Britain’s Medical Research Council, a publicly funded government agency, was published Wednesday in The Lancet.

“Our study is the first to link a genetic cause of weaker breathing muscles with sudden infant death syndrome, and suggests that genes controlling breathing muscle function could be important in this condition,” Dr. Michael Hanna, a researcher at the MRC Center for Neuromuscular Diseases and the University College London Institute of Neurology, said in a press release.

Also called “crlb death” or “cot death,” SIDS is a leading cause of death in this age group in high-income countries, including about 2,000 in the United States each year, according to the National Institutes of Health.

The phenomenon had thought to be associated with the position babies sleep in, including on their stomachs, and second-hand exposure to cigarette smoke, according to Hanna.

“There’s a big campaign in America and in Europe called the Back to Sleep campaign that’s been running for some years,” Hanna told CNN. “Basically, just the act of putting a baby on their back to go to sleep instead of the front reduces the incidence of these deaths by about 60 percent.”

The researchers found mutations in four of the 278 children who had died of SIDS and nine of the 729 healthy controls. All of the children had European ancestry, including 84 from Britain and 194 from the United States who had died.

“This international collaborative UK-USA study provides interesting new evidence for a possible link between respiratory muscle sodium channel dysfunction and SIDS. Further research is needed to confirm these findings and to evaluate any potential clinical relevance,” Dr. Michael Ackerman, a study co-author and researcher at the Mayo Clinic, said in an MRC press release.

The research team included scientists from the the Mayo Clinic, University College London, St. George’s University of London King’s College, University of Bristoland University of Edinburgh in Britain and Copenhagen University Hospital in Denmark.

The researchers examined the prevalence of mutations in the SCN4A gene, which is an important cell surface receptor that controls breathing muscles. They are low at birth and increase over the first two years of life.

Mutations have been associated with genetic neuromuscular disorders, including myotonia, periodic paralysis, myopathy and myasthenic syndrome as well as life-threatening pauses in breathing. Vocal cords spasms make breathing or speaking temporarily difficult.

The genes of the tissue from each group were analyzed to identify whether they had a mutation in the SCN4A gene. They also wanted to see if mutations affected the cell surface receptor that the gene codes.

They found general mutations in the SCN4A gene in six of the infants who died and nine of the controls. But only four among those with SIDS had disrupted the cell surface receptor.

The authors theorized that the mutation could weaken the breathing muscles in these children. And the child might not be able to correct their breathing, cough or catch their breath if other factors are involved such as tobacco smoke, getting tangled in bedding, a minor illness or a breathing obstruction.

However, the study looked at only one ion channel and it affected only 1.4 percent of the infants who died of SIDS.

“The respiratory muscles probably have about a hundred different ion channels that are ultimately responsible for normal contraction and relaxation of respiratory muscles. We’ve just looked at one channel because that was where our hypothesis took us,” Hanna said to CNN.

The authors noted that sodium channel blockers such as mexiletine can reduce the frequency and severity of myotonia in at-risk patients. Also they noted that acetazolamide may be effective to abolish attacks of respiratory and bulbar weakness in a patient with myasthenic syndrome.

“While there are drug treatments for children and adults with genetic neuromuscular disorders caused by SCN4A gene mutations, it is unclear whether these treatments would reduce the risk of sudden infant death syndrome, and further research is essential before these findings can become relevant to treatment,” Hanna said.

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