Newborn babies across England are being offered blood tests for a rare and potentially fatal metabolic condition.
Medium Chain Acyl CoA Dehydrogenase Deficiency (MCADD) affects the body's ability to break down fat for energy, especially when someone is ill or has not eaten for several hours.
It can usually be easily managed once diagnosed, but is often only spotted once the sufferer is seriously ill. Those with the condition can even die unless they receive glucose.
The family of schoolgirl Katy Frost did not know she had the disease until she collapsed during a school activity holiday aged of 10 and her organs began to fail.
Her parents were told she may die, but Katy, now 13, was eventually diagnosed and given treatment which enabled her to recover.
Katy's mother, Cora Durkan, from Haywards Heath, West Sussex, said: "We were lucky that she survived.
"That's the reason for the screening programme, MCADD can kill. However easy it is to manage, when it goes wrong, you can die."
Midwives, usually on a home visit, will take a pin prick blood sample for the test - which has been added to those for cystic fibrosis, sickle cell disease, the genetic disorder phenylketonuria and congenital hypothyroid.