By Conard Holton
"Many genetic conditions affect the development of the face," says professor Peter Hammond of the UCL Institute of Child Health (London, UK; www.ich.ucl.ac.uk). "While faces characteristic of Down's syndrome can be easily recognized, there are other, rarer conditions such as Williams syndrome, which results from an alteration on chromosome 7. This makes the temples narrower, the mouth fuller, and the jaw smaller."
Hammond has developed software that compares a 3-D picture of a child's face with other faces, to see which abnormal face fits most closely. The image of the abnormal face is a composite of between 30 and 150 children with that condition. Each image contains approximately 25,000 points on a face surface, capturing contours in 3-D. "The software can reduce the number of possible genetic tests given to each child," says Hammond.
There are more than 700 genetic conditions associated with characteristic facial features. Fragile X is the most common form of inherited mental impairment. Children with the condition have longer, narrower faces, with bigger jaws and ears that protrude very slightly. Smith-Magenis syndrome produces a nose with a flat bridge and an upper lip that appears lifted from the inside.
Hammond's software has identified Fragile X faces with an accuracy at 92%, Smith-Magenis syndrome at 91%, and Williams syndrome at 98%. Hammond envisages a future in which doctors take 2-D pictures of children's faces and e-mail them to a specialist center that converts them to 3-D, compares them with model faces, and e-mails back suggestions about which genetic tests to perform. Trainee clinical geneticists in Cambridge, UK, will benefit from the technology for the first time in January next year.
