A rare gene mutation that causes respiratory muscle dysfunction is said to be over-represented in infants who fall victims to the condition known as sudden infant death syndrome, according to a new study. But the most important thing to prevent death is to respect the recommendations.
Some cases of sudden infant death could be partly genetic, according to a new US-British study published on March 29, 2018 in The Lancet. The presence of this mutation could affect the ability of the respiratory muscles to act quickly in response to a lack of oxygen.
Sudden Infant Death is the sudden unexpected death of a child under 2 years of age – often less than 6 months – for whom no identified cause is found. In developed countries, the number of cases has dramatically decreased since the late 1990s, when health authorities advocated for caregivers and parents to put their babies to sleep on their backs and not on the stomach or side. Sudden infant deaths are estimated at about 300 per year in Britain.
In 2015, there were about 3,700 sudden unexpected infant deaths (SUID) in the United States according to the Centers for Disease Control and Prevention (CDC).
1.4% of sudden infant deaths related to a rare genetic mutation
Muscular canalopathies are rare genetic diseases, caused by a number of genes one of which is called SCN4A. This gene is crucial for the action and reactivity of the associated muscle. When it is altered by mutation, it causes periodic paralysis and has shown in particular to be able to cause in infants with brief episodes of myotonia (difficulty relaxing a muscle after a voluntary contraction) respiratory muscles causing life-threatening apnea.
Since these respiratory dysfunctions are compatible with the mechanism of sudden infant death, the researchers wanted to verify a potential link. “Most experts agree that respiratory failure during sleep is the leading cause of infant mortality” in sudden infant death, commented Stephen C Cannon, Professor at the Department of Physiology in Los Angeles in The Lancet.
The researchers examined the presence of this mutation in 278 children who died of sudden infant death as part of this study, as well as 729 healthy adult whose ethnic origins corresponded, to determine whether any mutations found were specific to death cases and not to a category of population. As a result, 4 of the cases studied (1.4%) had a SCN4A gene mutated to disrupt respiratory function, compared with none of the 729 controlled adults.
In the general population, this mutation of the SCN4A gene is very rare: it is estimated that it is found in fewer than five people out of 100,000, which is much lower than the rate of 4 out 278 found in subjects with sudden infant death, showing that this mutation is over-represented at home. Statistically, these results are sufficient to prove a direct link between this gene and some rare cases of sudden infant death.
“Our study is the first to associate sudden infant death with respiratory muscle weakness whose cause is genetic, but further research will be needed to confirm and understand this link,” said one of the authors of the study, the British professor Michael Hanna, quoted by The Lancet. Only limitations of the study: the subjects were all European and Caucasian, and therefore not representative of all possible ethnicities, and the anonymity of the recovered samples prevented the authors from verifying the presence of the mutated gene in the members of the family.
The most important thing is to respect the recommendations in regards sudden infant death
However, even if this link exists, which requires more research, it does not explain alone the occurrence of these deaths, emphasize the authors. For death to occur, there must probably be “a convergence of factors,” they write, namely a vulnerable infant, and an external stressor during a critical period of development. Thus, the mutation of the SCN4A gene would be a factor that “exacerbates” the infant’s vulnerability. Hence the importance of respecting the recommendations to prevent sudden infant death: put the babies on their backs and avoid sleeping in the parents’ bed.