The symptoms of autism in boys who have fragile X syndrome differ from those in boys who have autism alone, according to a study published 11 January in theJournal of Autism and Developmental Disorders1.

About one-third of people with fragile X syndrome are diagnosed with autism. However, the new study suggests that the autism symptoms that accompany fragile X syndrome may be subtly different from those seen in autism alone. 

For example, boys with fragile X syndrome tend to be interested in social interaction, but experience anxiety that results in their shying away from social contact. This would manifest as a social deficit on a diagnostic test, but it reflects a different underlying cause than do the social deficits seen in autism. This means that treatments developed for fragile X syndrome may be less applicable to autism than some people have hoped, the researchers say. 

In the new study, researchers looked at 49 boys with fragile X syndrome, 40 of whom have a diagnosis of autism, and 39 boys who have autism alone, all between 4 and 10 years of age. They analyzed two in-person diagnostic assessments for autism, the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised, to assess the boys' social behavior.

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