It was all the rage in Victorian times, but the once-popular notion that you can judge personality, intelligence and even criminal intent from the face or the shape of the skull has long since been discredited by research.

If physiognomy and phrenology are now rightly regarded as pseudo-science, however, the study of faces for clues to health is now making a medical comeback, in the diagnosis of inherited disease. This time it has sound science behind it.

Although most people can recognise the typical features of people with Down’s syndrome, it is not often understood that there are more than 700 other genetic conditions that shape the face in characteristic ways.

The mutations that underlie them also affect the spacing of the eyes, the position or shape of the ears, the prominence of the mouth and jaw, and the width and length of the face. Such features can be a valuable aid to identifying rare and serious disorders, but even medical specialists find many of them difficult to spot.

A new computer system designed by British scientists is now promising to revolutionise the diagnosis of these conditions. It uses three-dimensional photography to map children’s faces, to point clinicians towards rare conditions that they might never otherwise have considered.

The software, developed by Peter Hammond, of the Institute of Child Health, at University College London, can already diagnose more than ten genetic disorders in children with more than 90 per cent accuracy, and it is being fine-tuned to detect more than 20 others. The intention is to provide clinical geneticists with a powerful new tool for screening children with unexplained medical conditions, highlighting potential genetic syndromes that can then be confirmed with molecular tests.

“If you’ve got a child with an unknown condition, you can screen the face and reduce the number of genetic tests you need,” said Dr Hammond, a computer scientist. “For the NHS, the benefit would be that you are doing much more focused genetic testing, and these tests can cost in the order of £500 to £1,000 apiece.

“For the child, earlier diagnosis means they can get appropriate care earlier, and they can be monitored for other effects known to be associated with their condition. Children with Costello syndrome, for example, are prone to tumours, so they need to be imaged every six months to one year.

“Perhaps the biggest advantage is for the parents. It’s very stressful not to know what your child has got. For very small children, you don’t know what the prognosis is. And also, the family will want genetic counselling. They want to know the risk to any future children they might have.”

The system, which will be presented today at the British Association Festival of Science in York, also has important applications in medical research and training. Scientists have used it to find genes that are involved in Williams syndrome, which generally causes heart and blood vessel defects, and to discover a cranial abnormality that affects some children with autism, yet is invisible to the naked eye.

Later this year, the software will be used on trial in the specialist teaching of clinical geneticists. The system uses 3-D cameras to take a high-resolution image of a child’s face, which the software then compares with composite images built up from dozens of faces of people with particular conditions.

For Williams syndrome, which affects between one in 10,000 and one in 20,000 births, it is 98 per cent effective at identifying children who have already had it diagnosed. Their faces are narrower and they have a shorter, upturned nose, an upturned mouth and a smaller jaw. “Children with Williams syndrome also have a very endearing quality,” Dr Hammond said. “They are super-friendly.”

Other conditions that can be identified with more than 90 per cent accuracy include Smith-Magenis syndrome, which affects one in 25,000. It causes behavioural problems such as aggression and an inverted sleep cycle. The bridge of the nose is flat and the upper lip is uplifted.

Children with Jacobsen syndrome, which affects one in 100,000 and causes heart defects, eye defects and learning disabilities, have eyes that are farther apart than normal. A more common condition, Fragile X syndrome, affects one in 4,000 boys and causes learning disabilities and behavioural symptoms like those of autism. Such children have elongated faces, which look superficially normal and are hard to identify. “The face is very subtly different,” Dr Hammond said. “It is longer and narrower, the ears stick out a bit more and the jaw, as they get older, tends to get bigger.”

About 15 to 20 British hospitals have the 3-D cameras needed to image a child’s face for screening. The system would be useful for inexperienced doctors who have seen few cases of rare genetic disorders, and for diagnosis in ethnic-minority groups, whose underlying facial structure can complicate recognition of typical features.

Times Recommends

• Revealed: how Eurocrat leaked secrets over dinners
• Politicians use the net to brainstorm
• British spy in longbow plot to kill Himmler