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Facial features provide clue to autism severity

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Deborah Rudacille
20 October 2011

Face map: Boys with autism have broader faces and mouths, flatter noses and narrower cheeks than controls do.

Boys with autism have a distinct facial structure that differs from that of typically developing controls, according to a study published 14 October in Molecular Autism1.

Specifically, boys with autism have broader faces and mouths, flatter noses, narrower cheeks and a shorter philtrum — the cleft between the lips and nose — compared with controls, according to the three-dimensional facial imaging system used in the study. These distinctive features suggest that certain embryonic processes that give rise to facial features are perturbed during development, the researchers say.

The participants in the study were all 8 to 12 years old, an age range during which the face is relatively mature, but not yet affected by the hormonal changes of puberty.

The researchers used the imaging system, dubbed 3DMD, to plot 17 ‘landmarks’ or coordinates on the face of 64 boys with autism and 40 typical controls. They then measured the distance between several of these coordinates.

Boys with autism who have the most distinctive facial features cluster into two groups with very different sets of autism symptoms, the researchers found.

Boys in one group tend to have wide mouths, combined with a short distance between the top of the mouth and the bottom of the eyes. They also show severe symptoms of autism, including language impairment, intellectual disability and seizures.

By contrast, those in the second group have broad upper faces and a short philtrum. They are more likely to be diagnosed with Asperger syndrome, and to have fewer cognitive impairments and language difficulties compared with the first group.

“As a clinical geneticist, I have always been impressed by a certain facial phenotype in children with autism,” says lead investigator Judith Miles. But it wasn’t until she turned to 3DMD, developed for use by plastic surgeons, that clear quantitative differences emerged between boys with autism and controls, she says.

Those differences almost certainly reflect underlying neurodevelopmental processes, she says. “The reason to look at the face is that it reflects differences in the brain.”

Group effects:

Studies have found that children with autism are more likely than controls to have dysmorphology, or unusual physical features, of the head and skull.

Earlier this month, researchers at the University of South Alabama reported that among children referred for genetic testing for suspected autism, those who have a copy number variation (CNV), a deletion or duplication of a genetic region, are more likely to have unusual facial features than those who carry no CNVs2.

“There is remarkable etiologic heterogeneity in autism, and the use of dysmorphology phenotyping may help us come to grips with some of this complexity,” says Curtis Deutsch, associate professor of psychiatry at the University of Massachusetts Medical School, who was not involved with either new study.

Studies of facial dysmorphology in autism have generally relied on observation or tools such as calipers to pinpoint specific facial features.

3DMD instead uses multiple digital cameras to capture a 360-degree image of the head. Algorithms integrate the images to produce a single 3D image that is analyzed using special software.

This generates results that are more fine-grained than manual measurements, says Kristina Aldridge, assistant professor of pathology and anatomical sciences at the University of Missouri.

“We’re not talking about kids you would pick out on the street as looking different. These are subtle differences that are systematic, [in the range of] 2 to 5 millimeters,” Aldridge says. “It is extraordinarily precise.” She has used 3DMD to assess facial dysmorphology in children with birth defects3.

Deutsch has used the same technology in his own research. Still, he cautions that the sample size in the study may not be large enough to generate reliable results.

“It is also important to guard against performing a multitude of statistical tests without appropriate corrections,” he adds. “Otherwise differences that are reported as significant can result from chance alone.”

Researchers typically apply mathematical formulas to correct for chance associations. Miles instead used cluster analysis, which pulls together similar entities from large datasets.

This sort of analysis can produce results that are difficult to interpret, Miles says. “It will always give you something, but we had to look at whether clinical differences correlated with the subgroups identified by the cluster analysis.”

Using autism diagnostic characteristics, intelligence quotients (IQ), medical symptoms and other measures, she says, “what we found is that those two subgroups really do appear to be discrete clinically.”

The findings resonate with researchers who have studied dysmorphology in autism using less sophisticated measures than 3DMD.

For example, a team at Baylor College of Medicine in Houston, Texas, reported at the 2011 International Meeting for Autism Research in San Diego that severe autism symptoms predict the presence of dysmorphic features — albeit those not discernible to the naked eye. “The vast majority of cases [in that study] show very subtle facial differences,” says Robin Kochel, assistant professor of psychology at the Baylor College of Medicine.

The results of the new study jibe with what she sees everyday in the Autism Center at Texas Children's Hospital, Kochel says. "Those who have more dysmorphology tend to have more problems and be more severely affected."

References:

1: Aldridge K. et al. Mol. Autism Epub before print (2011) PubMed

2: Gannon W.T. et al. J. Dev. Behav. Pediatr. 32, 600-604 (2011) PubMed

3: Martinez-Abadias N. et al. Dev. Dyn. 239, 3058-3071 (2010) PubMed

Comments

Name: Jon Brock
21 October 2011 - 11:07AM

This paper is available to download (open access) at http://www.molecularautism.com/content/pdf/2040-2392-2-15.pdf

I've just been looking through and it's really interesting. It's worth highlighting the fact that most of the ASD boys were indistinguishable from the controls (at least using these metrics). What the study does do very nicely I think is highlight the importance of looking for subgroups within autism.

The authors do make a slightly odd comment, which is that at a group (rather than subgroup) level, the autistic boys were different from the typically developing, and that this may correspond to the "beautiful face" mentioned by Kanner. Given that they identify different subgroups, I don't think it makes much sense to even consider what the average autism face means. In any case, I think it's fairly well established that faces that are closest to the average of the typical face are perceived with high rater agreement to be the most beautiful. So I would have thought that any autistic boys with "beautiful faces" would, if anything, have been right in the middle of the typically developing boys.

Name: Deborah Rudacille
21 October 2011 - 2:10PM

Thanks for the comment, Dr. Brock. The clinicians I spoke with stressed that the alterations were very subtle but that together they produced a pleasing appearance--broad smiles, widely spaced eyes etc. These are not features that most lay people would consider 'dysmorphic' per se. But the 3DmD measurements do appear to bear out clinical observations going all the way back to Kanner that the faces of boys with autism are distinctive in some some way.

Thanks for reading SFARI.org!

Name: acommentonthis
7 January 2013 - 4:18AM

but what about girls with autism?

Name: whatever
2 November 2013 - 7:07PM

WHAT ABOUT GIRLS?!

Name: Aspie brother
23 March 2014 - 11:50AM

I have a brother who has Aspergers. I ve always thought he looked slightly different but couldn't pinpoint why, as in he doesnt have unusual features but if you seen him once you won't forget how he looks like cos his look is slightly distinctive.

I do notice his eyes were wider apart and he has a round face that looks very boyish (he is 23).

Now I realized he has the features described in this study: a broad mouth, a very very short philtrum and a broader upper face. He is very high functioning, so I think he fit the second group described in this study perfectly.

Name: Nordlys
8 December 2014 - 2:32PM

And those are also children. All children and teenager are disproportionate, because they're developing. Studies should make sense only on adults.

Name: autistic female
12 November 2014 - 5:38AM

This is completely useless information as youve only studied boys. I have been diagnosed with autism. I am a female. You could at least TRY doing research that helps everyone instead of going with the false stereotype that "only boys have autism". Girls get it too. I have been diagnosed officially. I do have pointy features. But you only have half of the picture because you only studied boys. Wake up.

Name: Nordlys
8 December 2014 - 2:30PM

Do you mena I have also different facial features other than different personality? That sucks!

But, what about identical twins - one NT and the other autistic? They have the same gene, so they should be identical.

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