Very occasionally, young babies die unexpectedly in their sleep with no obvious cause or explanation. The condition is known as sudden infant death syndrome (SIDS) and is poorly understood, although it’s thought that various environmental factors might play a role. Now, researchers have uncovered a genetic component that could explain some instances of SIDS.

About 1,400 babies in the US die from SIDS each year and scientists are working hard to better understand its causes so that at-risk babies might be protected from it in future. Two factors thought to be involved in SIDS are being born prematurely and a low birth weight, both of which might make babies particularly susceptible to environmental stressors. These include tobacco smoke, mild illnesses, getting tangled in bedding, and obstructed breathing.

Sudden death is linked to how the body reacts to these stressors, with problems arising with heart rate, breathing, or temperature regulation. But it seems genetic mutations might be to blame too – at least in some cases of SIDS. Last year, researchers found a link between a genetic mutation that weakens the breathing muscles and SIDS. Now, a different team has identified another possible genetic cause.  

Researchers from the University of Washington think that a genetic mutation that disrupts how the body processes lipids (e.g. fats and cholesterol) is linked to SIDS. An inability to break down the fats found in milk could lead to a build-up that then interferes with heart function, causing the heart to stop suddenly. The team’s findings are published in the journal Nature Communications.

The abnormality in question is known as mitochondrial tri-functional protein (MTP) deficiency, a rare illness that prevents the body from converting fats into energy. This is due to a lack of activity in the enzymes that normally break down fat and involves a rare mutation in a gene called HADHA.

"If a child has a mutation, depending on the mutation the first few months of life can be very scary as the child may die suddenly," said first author Jason Miklas in a statement. "An autopsy wouldn't necessarily pick up why the child passed but we think it might be due to the infant's heart stopping to beat."

Miklas, who completed his PhD at the University of Washington, was inspired by a small study that found that children who had difficult-to-explain heart disease could not properly break down fats. In the new study, the team grew heart cells derived from stem cells in a dish, some of which were genetically modified to have a mutation in the HADHA gene. While the cells without the mutation developed normally, those with the mutation could not maintain a regular heartbeat and were unable to properly process fatty acids.   

At the moment, there is no cure for MTP deficiency, but the researchers hope their findings could lead to better identification and treatment of babies at risk of SIDS in future. Parents could be screened to see if they are likely to have a child that carries the rare mutation, for example.

The researchers are now looking into a drug called Elamipretide, which is used to stimulate the heart and other organs if they are lacking in oxygen. They hope the drug might have potential in the treatment of struggling infant hearts too.

“It's very exciting to think that our work may contribute to future treatments, and help for the heartbreak for the parents who find their children have these mutations," said Professor Hannele Euohola-Baker, who led the research.