Rare genetic mutations linked to sudden infant death syndrome

Rare mutations in a gene that controls muscle function may contribute to some cases of sudden infant death syndrome (SIDS), according to new research published in The Lancet.

SIDS, also known as cot death, typically affects infants between two and four months old and is one of the leading causes of infant death in developed countries. The exact causes of SIDS are not fully understood, although it is associated with premature birth and low birth weight, according to the NHS. 

This latest research compared the DNA sequences of 278 infants who died as a result of SIDS with the DNA sequences from 729 healthy adults. This comparison identified four mutations only found in in the sequences of babies who had died from SIDS, all affecting the function of a gene called SCN4A. 

This gene codes for a protein that allows sodium to enter the cells and cause the muscle to contract. In the wider population, these mutations are very rare, occurring in only five in 100,000 people. Further work using cells in the lab showed that these four mutations prevented the SCN4A protein from functioning correctly.

'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,' said Professor Michael Hanna of the National Hospital for Neurology and Neurosurgery and University College London, the study's senior author. 'However, more research will be needed to confirm and fully understand this link.'

Dr Emma Matthews, also from the National Hospital of Neurology and Neurosurgery and another author of the study, said that SCN4A mutations are not likely to cause SIDS on their own. 'We think the genetic mutations we found may have contributed to why some of these infants died but are likely to have interacted with other risk factors and would not necessarily be the sole cause of death.' 

Although large public health campaigns have reduced the number of SIDS cases dramatically, 300 infants still die from SIDS every year in the UK. Francine Bates, chief executive of the Lullaby Trust, a charity raising awareness of SIDS, welcomed the study, but urged parents to continue following best practice for avoiding cot death.