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It remains one of the greatest mysteries of medicine. Although autism will be diagnosed in more than 25,000 U.S. children this year, more than new pediatric cases of AIDS, diabetes and cancer combined, scientists and doctors still know very little about the neurological disorder.

Unlike childhood diabetes or pediatric leukemia, there is no blood test, no scan, no image that can detect autism. Diagnosis relies totally on behavioral observation and screening. And that's not easy.

According to the National Institute of Neurological Disorders and Stroke, three distinctive behaviors characterize autism: lack of social interaction, problems with verbal and nonverbal communication, and repetitive behaviors or narrow, obsessive interests. But children with autism display these symptoms in many different ways, some as mild as avoiding eye contact, while others are totally immersed in a world of their own.

Dr. Gary Goldstein, president of Kennedy Krieger Institute, one of the leading U.S. facilities for autism research and treatment, says although doctors know more about autism than ever, plenty of questions remain unanswered. Over the past few years, it has become clear that genetics play a big role in the development of autism. But researchers believe something -- a trigger -- sets off autism in a child.

"It's a combination of being genetically vulnerable, and then having some kind of social or toxic exposure that tips you over," Goldstein says. If scientists find that trigger, they could find the missing piece of the autism puzzle. Read full article »

Val Willingham is a producer with CNN Medical News.

All About AutismCenters for Disease Control and Prevention

Unraveling the mystery
CNN reports on the impact and latest science concerning the developmental syndrome of autism in a global investigation.
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