Ondine's Curse hits people while they sleep
Scientists have found the gene responsible for the rare condition Ondine's Curse - where sufferers 'forget' to breathe.
The condition is named after a mythological story.
Some accounts say the water nymph Ondine was punished by the gods after falling in love with a knight by being condemned to stay awake in order to breathe.
The condition, where the central nervous system fails to control over breathing while asleep, was identified 30 years ago, and there are an estimated 400 sufferers worldwide.
We will be able to offer prenatal diagnosis
Dr Jeanne Amiel, Researcher
Currently, they need to rely on ventilator support to help them breathe.
Children need to be on a ventilator all the time. By the time they reach adulthood, they only need it while asleep - when sufferers are most likely to have problems breathing.
They also have to undergo tracheotomies, where an opening is made into the windpipe.
The French team who discovered the gene say it could lead to therapies and prenatal diagnosis in the future.
Their findings will be presented to the European Society of Human Genetics in Birmingham on Tuesday.
The gene responsible for the condition is called Thox2B.
Research in mice had suggested it could be linked to the condition.
The team from the Hopital des Enfants Malades in Paris then looked at 43 patients with Ondine's Curse, and compared them to 250 people who did not have the condition.
They analysed DNA samples, and found those with Ondine's had mutations of Thox2B.
Dr Jeanne Amiel told BBC News Online: "We don't know yet what the effect of this mutation is.
"But we know it is disease-causing."
The mutation is not present in the parents of children with Ondine's Curse, so it must occur in the foetus.
But when the affected child grows up, if they have children, they will also be affected.
Dr Amiel said: "The first thing this discovery allows us to do is to confirm the diagnosis of Ondine's Curse by molecular testing.
"The second thing is that we will be able to offer prenatal diagnosis."
She said researchers would also be able to replicate the condition in mice, which would allow them to begin to look at what drugs could treat the condition.
The research has also been published in the journal Nature Genetics.