Scientists have discovered the gene fault which causes a rare but disabling syndrome.
Victoria Peaford (right) has the rare syndrome
Cornelia de Lange Syndrome can cause impaired development, twisted bowels and missing hands and fingers.
An international team of scientists including experts from Newcastle's Institute of Genetics, carried out the research.
The finding, published in Nature Genetics, could lead to genetic and prenatal tests for the syndrome.
In the past, many of those affected by CdLS died in childhood, but most now live to adulthood.
Researchers in this study analysed the DNA of 12 families who had more than one member with CdLS.
They identified a large gene on chromosome 5, which they named NIPBL where mutations giving rise to Cornelia de Lange syndrome occur.
The gene regulates biological signals that have wide ranging effects on a variety of organs during development.
Professor Tom Strachan, director of the University Institute of Human Genetics at the International Centre for Life, in Newcastle, told BBC News Online the gene sequence had been baffling scientists for years.
"We have been studying this for about nine years, but there has been a problem in trying to find the underlying gene.
CORNELIA DE LANGE SYNDROME
CdLS affects around one in 10,000 children
At birth CdLS babies are usually smaller than normal
They usually have small hands and feet and may have hands or fingers missing
Their development may be slower than normal
Children with the syndrome have a distinctive appearance, with eyebrows which look as if they have been pencilled onto the face meeting in the middle, eyelashes which are unusually long and curled and an unusually small nose
The syndrome was named after a professor of paediatrics in Amsterdam who
published a paper on the condition over 60years ago.
"When you see a genetic condition you can normally study it in families and see how it moves from
one affected individual to another."
But he said that because CdLS was so complex and debilitating and led to such serious handicaps that parents often only had the one child and affected individuals typically did not have any children of their own.
He said the new information would enable genetic tests to be carried out so that clinicians could give an accurate diagnosis to parents as well as offering them practical information during any future pregnancies.
Professor Strachan added: "We now want to understand what goes wrong and how it goes wrong in development.
"We hope to be able to design something that can be given to mums as a supplement to ensure babies they are carrying with the condition have it in a less severe form.
"CdLS causes serious problems and even if we could give some kind of supplement to parents to lessen the mental retardation then it might mean the difference to them about whether to carry on with the pregnancy."
Being able to diagnose the condition in pregnancy might also bring some relief to parents as many may not be carrying a second child with CdLS.
But Professor Strachan said he was "frustrated and concerned" that the research into CdLS was being hampered by a serious funding crisis because it affects such a small number of people. The current funding runs out in 2005.
"I feel that as a society and nation we are letting these children and their parents down."
Alan Peaford, chairman of the Cornelia de Lange Syndrome Foundation for the UK and Ireland, whose daughter Victoria is affected by the condition, praised the work done by the Newcastle scientists.
He said: "Knowing this means that doctors will be able to diagnose the condition right, and that is fantastic.
"We have been waiting for about 15 years to get
the call from the scientists telling us that this is possible."
"The diagnosis will also help save lives, because many of these children suffer from twisted bowels which can be a killer and if the parents know that their child has CdLS they know what to look out for.
"It will improve the medical care and attention and it will save lives."