Update on Ectodermal Dysplasia Face Study

December 2007
By Peter Hammond, Molecular Medicine Unit, Institute of Child Health, UCL; and Neil MacBeth, Eastman Dental Institute, UCL

At the NFED Family Conference held in St Louis in 2007, Peter Hammond’s research assistant, Matt DiFranco, and Eastman Dental Institute prosthodontist Neil MacBeth took photographs with a special 3D camera from University College London (UCL). In all, 37 families volunteered to have 3D face images recorded, primarily affected children and adults but also siblings and parents so that family likeness could be captured. Previously, photographs had been taken in London of UK families with individuals who were also affected by ED.

Professor Hammond has used 3D images to study facial form and growth in a variety of genetic conditions that cause differences in face shape. In collaboration with medical doctors and other computer scientists, he has been able to identify even minor face shape differences very accurately. It is already known that the faces of individuals with ED are subtly different from the general population and we hope that the differences we detect might assist in the diagnosis of individuals with a mild presentation of the condition. Although similar analyses have been carried out using X–ray and land marking studies on ED patients, this is the first study using the latest surface based analysis.

The 3D camera captures as many as 20,000 points on a face producing a very accurate map of its surface contours. Using software developed at UCL, a collection of 3D face surfaces of individuals with the same genetic syndrome can be combined to find an average or typical face for that condition.

The first two images above show a portrait and a profile of the average face of 29 male individuals with ED. The second pair shows the same views of an average face of 127 male individuals with no known genetic condition and with a similar average age. By eye, there are obvious differences in the shapes of these two average faces. But a computer-based analysis can detect much more subtle differences as the figure below demonstrates where the color coding shows differences in the mid-face but also on the chin, above the eyelids and on the ears.

Areas of the average ED face that are colored red are at least 5 mm smaller or inside corresponding regions of the average face of unaffected males, and those colored blue are at least 5 mm larger or outside. Green areas are where the two average faces coincide. Colors in between these extremes on the red-green-blue spectrum correspond to differences within the [-5,+5] range.

Once we have carried out a statistical analysis of the images, we can also model the growth of the face. For example, the graph below suggests that the faces of boys with ED may grow at a similar rate as the general population up to the age of about five years, but at a slower rate subsequently. This could have implications for treating hypodontia patients, as it may influence the timing of intervention treatment and the choice and design of the prostheses used to replace the absent teeth. It may also raise awareness of the effect of treatment on the facial appearance.

By making a model of the average face shape of children with a confirmed diagnosis for ectodermal dysplasia and comparing it with the average of a control group of children of a similar age, we expect that the more subtle facial characteristics of the condition will be readily detected. Later, we will use the model to determine how similar an individual’s face is to the average ED face, or to the average control group face and assist with the diagnosis of ED in difficult cases.

We would like to thank everyone who volunteered to have their picture taken and we look forward to providing a final summary of the results once they have been published in an appropriate medical journal.

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