The shape of the face and the size and position of the eyes, ears, nose and lips can point to a wide range of genetic illnesses – from rare disorders of the heart and brain to more common conditions like autism.

The differences in the features of normal and abnormal children are often so subtle very experienced medical specialists can often only detect them – and diseases can often only be diagnosed with expensive and time-consuming DNA tests.

But now researchers at London's Great Ormond Street Children's Hospital have developed a new computer programme that can home in on the tiniest variations in face shape and features.

Prof Peter Hammond, a specialist in computational biology at the Institute of Child Health at University College London, said it could revolutionise diagnosis and treatment of conditions affecting tens of thousands of people.

"Some conditions are very obvious for example you can spot a kid with Down's Syndrome a mile away but there are over 700 genetic conditions that involve unusual and often very subtle facial characteristics," he said.

"These are sometimes called heart and face syndromes because the development in the embryo of the heart, the face and the brain are closely linked – and that's why if there's something unusual about the face this is often also seen in the brain or the heart.

"Affected children may have eyes set further apart, ears set lower on the head, a shorter nose, fuller lips, a larger tongue or a mouth narrower than in children of typical development."

Prof Hammond and colleagues at UCL have developed a programme that can make a super-accurate three-dimensional copy of a child's face using 25,000 reference points to construct every minor contour.

The images are then digitised and automatically checked with a database of thousands of different face shapes to determine whether there is a match with known genetic conditions.

"So far the system has been programmed to identify 30 different conditions with an accuracy rate of 90 per cent.

"When our computer identifies a face it should speed up the whole diagnosis process which can be drawn out and expensive – and this should benefit the child and the parents," said Prof Hammond, who will report his findings today to the British Association for the Advancement of Science's conference in York.

"Some of these conditions have a profound effect on the child and the child's family who want a diagnosis as quickly as possible because they want to know what the risks are to any future children.

"For example a child could have a potentially difficult heart condition which we might otherwise miss, important medical treatment could be delayed and in
situations where an illness leads to unusual behaviour it's better to start training while the child is still young so to avoid certain situations."

The system is already being used as a training aid to help paediatricians recognise some of the more obscure genetic conditions that are seldom seen even in specialist hospitals and are therefore difficult to recognise.

Apart from autism a range of illnesses are being targeted.

These include Fragile X Syndrome, an autism-like disease which leads to learning difficulties and retarded language skills and Williams Syndrome, characterised by heart conditions, learning difficulties and extreme friendliness.