Researchers from the Boston-based Autism Consortium have discovered a rare chromosomal abnormality reported to be 100 times more common in children with autism. The study, published last week in the New England Journal of Medicine, found that in approximately 1 per cent of autism cases a small part of chromosome 16 is either duplicated or missing.
Autism - along with several related conditions together known as autistic spectrum disorders - is a lifelong developmental disability that typically appears during the first three years of life. The disorder affects social and language skills, and the way in which a child relates to people, objects and events. Although autism often runs in families, many children are born to parents with no history of the condition.
In the new study, the researchers looked at DNA samples from more than 1,400 affected individuals and a similar number of their unaffected parents. They found that five of the affected individuals were missing an identical piece of chromosome 16, which was intact in their parents - indicating that the genetic glitch had occurred spontaneously, rather than being inherited.
To confirm their findings, the team studied almost 1000 patients from the Children's Hospital Boston, around half of whom had been diagnosed with autism or a related developmental disorder. They identified another five children with the same missing piece of DNA, and a further four with a duplication of the same region.
'While epidemiologic studies indicate a very large genetic component to autism, little is known about how specific genes are involved', said senior author Mark Daly, of the MGH Center for Human Genetic Research. 'We're still a long way from understanding how this chromosomal deletion or duplication increases the risk for autism, but this is a critical first step toward that knowledge', he added.
The study adds to growing evidence that so-called structural variation - variable sections of DNA that may be flipped around, missing or duplicated in different individuals - play an important role in human health and disease.