Physical features of autism spectrum disorder (ASD)

Social and language issues dominate most of the discussion about the features of autism spectrum disorder (ASD).

A neglected area of study are the physical feature characteristics that have been known to be associated with ASD. Unlike some of the diagnostic physical changes in disorders such as Down Syndrome, physical features found in ASD are often subtle and missed by most clinicians.

Ozgen and colleagues from the Netherlands, UCLA and the UK recently published a case-control study of physical features in children with autism. They compared 224 children with ASD and normal intelligence to a matched pair child without ASD. A portion of the assessment was completed by raters blind to the diagnosis of the child.

The assessment included a variety of quantitative and qualitative assessments. For example, in the quantitative assessment category, boys (but not girls) with ASD had a smaller BMI indicating a lower weight to height ratio.

The most common structural (morphological) features found in the ASD children included:

* Sandal gap toes (59%)
* Facial asymmetry (46%)
* Abnormal non-frontal hair whorl (39%)
* High narrow palate (37%)
* Attached ear lobes (35%)
* Hypermobile joints (33%)

Some morphological features were found in the ASD that were absent in the 224 controls including:

* Brachycephaly
* Mouth asymmetry
* Eyes asymmetry
* Ear lobe crease
* Macrostomia (large mouth)
* Limited facial expression
* Open mouth appearance
* Abnormal whorl
* Prominent lower jaw

The authors note these minor physical characteristics were more common among the boys than girls in the study. These types of features have been described in other populations with copy number variations (CNVs). CNVs are an alteration of the genome with a complete loss of a gene copy, gain of a copy or disruption of a dosage-sensitive gene.

The authors note that these physical characteristics are unlikely to be incorporated into diagnostic features. However, they note that the features might be helpful in identifying relevant subgroups for further study. It is important to not bring too much attention to these features in individual children. Some features may add a level of social scrutiny to an already challenging clinical problem.

William Yates is a family physician who blogs at Brain Posts.

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