Genetic Impairment of Respiratory Muscles Linked to SIDS


Genetic impairment of respiratory muscles via the SCN4A gene may be linked to certain cases of sudden infant death syndrome (SIDS), according to a new study

"Further research is required to fully evaluate how common mutations in this particular gene will be in SIDS cases," said Dr. Michael G. Hanna of University College London and the National Hospital for Neurology and Neurosurgery.

"We have analyzed one muscle ion-channel gene in respiratory muscle, and it's known there are many more – these genes should now be evaluated as new potential candidate causes of SIDS," he told Reuters Health by email.

In their report, online March 28 in The Lancet, Dr. Hanna and colleagues note that contraction of respiration or skeletal muscles is controlled by the sodium channel NaV1.4, which is encoded by the gene SCN4A. Variants in SCN4A have been found in infants with a variety of conditions including myopathy, myasthenic syndrome and life-threatening apnea and laryngospasm.

To assess its possible role in SIDS, the team compared to tissue from 278 infants who had died from SIDS with that from 729 ethnically-matched adult controls.

The team found that four of the SIDS group (1.4%) had a rare functionally disruptive SCN4A variant compared to none of the controls. These variants, they write, "are predicted to significantly alter muscle membrane excitability and compromise respiratory and laryngeal function."

Dr. Hanna pointed out, "The full implications for clinical practice require further research – this should include evaluating the role of screening this gene in families who have had one cot death to assess future risk."

Furthermore, he added, "it is recognized that certain available drugs can improve sodium channel function and the place such drugs may have in preventing SIDS should be evaluated." Still, Dr. Hanna cautioned, "It remains essential that babies are always put to sleep on their backs."

Dr. Stephen C. Cannon of the David Geffen School of Medicine at UCLA, in Los Angeles, told Reuters Health by email that the study "identifies a new risk factor for SIDS, mutation of a sodium-channel gene that regulates skeletal muscle excitability."

"Two important implications of this discovery are that available pharmacologic agents may lower the risk of SIDS for some patients with this type of mutation, as has been shown for a related breathing problem of infants with severe laryngospasm," said the author. 

"And secondly that this study highlights the need for more research to understand the developmental changes in excitability of muscles that control breathing – a potential risk that we all share," said Dr. Cannon, who wrote an accompanying editorial.