Ped Med: Scientists study genes in autism

SAN FRANCISCO, Dec. 4 (UPI) -- Most mainstream scientists think there is a strong genetic component to autism that determines who will fall and who will stand strong in an encounter with an environmental health hazard.

In studies that give credence to the notion of autism arising from a nature-nurture nexus, Dr. Martha Herbert at Massachusetts General Hospital in Boston and colleagues found at least 51 overlapping genes that appear on two lists of suspects: those thought to raise the risk for the disorder and those that seem to increase the susceptibility to environmental exposures.

In addition, they noted children with autism spectrum disorders who had alterations in one or more of these 51 genes were likely to show a changed sensitivity to any toxins in their surroundings.

The ASD umbrella covers an array of conditions united by three main characteristics -- varying degrees of difficulty in socializing, communicating and imagining -- that typically appear before age 3, according to the official definition in the American Psychiatric Association's diagnostic manual.

Heredity -- and the interplay of as-yet-unidentified genes and environmental triggers -- may explain most of the wide variation in autism's manifestation, from near normal functioning in most settings to impairing disability, scientists speculate.

"Autism is the most heritable of all psychiatric conditions, with the heritability approaching 90 percent," said Dr. Daniel Geschwind, professor of neurology and psychiatry, director of the Neurogenetics Program and the Center for Autism Research and Treatment at the University of California, Los Angeles, School of Medicine and author of "Microarrays for the Neurosciences" (MIT Press, 2002).

"There's room for the environment, but not a lot of room," he added.

The search for genes at work in autism was pushed into overdrive by the milestone announcement April 14, 2003, that in a culmination of a 13-year effort, geneticists had sequenced the human genome, decoding the hereditary blueprint for a human being -- a feat many equated with man's landing on the moon.

The hope is that now that their scrambled script can be read, genes will provide some instructions on ways to prevent, treat and maybe even cure disorders like autism, researchers said.

To that end, a consortium of federal agencies and parent-founded advocacy groups has dedicated more than $10 million for genetic investigations of the disorder.

Most researchers suspect more than one gene -- and perhaps as many as 100, by some hypotheses -- is involved, likely in varying combinations in different individuals, though few would argue inheritance alone is responsible.

Genetic susceptibility to autism need not necessarily translate to the development of the disorder, while a healthy hereditary history may not guarantee immunity to it, scientists said.

Compelling clues have led to the general consensus that genes cannot be left out of the equation in the vast majority of cases, researchers said.

There is the suggestively greater prevalence of autism among the male sex. There are studies showing if one identical twin has autism, there's an approximately 75 percent chance the other will as well. Those odds plummet to 3 percent in the case of fraternal twins and to 2 percent to 6 percent for siblings in general, according to the Centers for Disease Control and Prevention in Atlanta.

Other family ties in autism also are coming to light with increased identification of the disorder in parents by way of their offspring, researchers said.

"We have a number of kids now that in the process of their being evaluated and diagnosed, their parents are being secondarily diagnosed," said Dr. Eileen Costello, a pediatrician at the Boston University School of Medicine and co-author of "Quirky Kids" (Random House, 2003).

"And almost to a family, every time I asked, 'Where do you think this came from in your child?,' there was something in the family history that pointed to a genetic etiology or at least a genetic component to where this came from ... other neurodevelopmental disabilities, seizure disorders, ADD (attention-deficit disorder), depression, other psychiatric illnesses, other things in the family," she told an autism conference sponsored by the Brookings Institution in Washington.

"People did not say, 'No idea. There's never been anything like this in my family before.'"

(Note: In this multi-part installment, based on dozens of reports, conferences and interviews, Ped Med is keeping an eye on autism, taking a backward glance at its history and surrounding controversies, facing facts revealed by research and looking forward to treatment enhancements and expansions. Wasowicz is the author of the forthcoming book, "Suffer the Child: How the American Healthcare System Is Failing Our Future," to be published by Capital Books.)

Next: A look at the kin of children with autism

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UPI Consumer Health welcomes comments on this column. E-mail: lwasowicz@upi.com