Newswise — According to the Centers for Disease Control, approximately 24,000 children each year are born with some form of autism. As scientists try to understand the disorder better, two University of Missouri-Columbia researchers have developed a new diagnostic tool that will help group children with the disorder into two subgroups, opening the door to more specific treatments.

"We found that by using two readily available tests, autism can be divided into two subgroups, 'essential autism' and 'complex autism' with different outcomes and recurrence risks," said Judith Miles, a professor of child health genetics. "It's very important for families to realize that autism is not a single disorder. Separating essential autism from complex autism should be the first diagnostic step for children with autism spectrum disorders as it allows better prognostication and counseling. Definition of more homogeneous autism subgroups will increase the power of research analyses."

Autism is a clinical diagnosis, defined only by the social, communication and behavioral impairments in a child. Recently, MU scientists have been looking for genetically relevant biological markers. Miles, and T. Nicole Takahashi, a senior research specialist at MU, found that 20 percent of the children in their study displayed dysmorphic physical features such as an abnormally small head or a malformed ear or hand. This group of children had different autism symptoms than the other larger group and was defined as having "complex autism." Children with complex autism were more likely to have lower IQs, seizures and remain functionally nonverbal after age 8.

Children with no physical malformations were diagnosed with "essential autism." These children were more likely to be male, have a family history of autism, and have a high risk for recurrence of autism in their immediate siblings.

"We're looking for what causes autism on a genetic basis," Miles said. "This is the groundwork for diagnosing the disorder better. By determining if there are differences between the children who have distinct physical markers such as a small head and those who don't, we can start to identify differences in their genes. Once you start splitting the disorder into subgroups, you start seeing specific trends and the water is not as muddy as it once was."

Grants from the Sears Trust, the National Institutes of Health, the Missouri Department of Mental Health and the National Association for Autism Research funded the five-year study. The American Journal of Medical Genetics recently published the study in their June 2005 edition. Miles believes that future research should focus on these two subgroups and identify additional categories within the subgroups.

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American Journal of Medical Genetics