Blood Test Can Identify Some Children With Strep-Related Behavioral Disorders

February 18, 1997

PROVIDENCE, R.I.--Scientists have developed what could be the first genetic test for a psychiatric illness.

The blood test uses a genetic marker of susceptibility to rheumatic fever to identify children with obsessive-compulsive disorders (OCD) and tic disorders, including Tourette syndrome, associated with strep-throat infections. The test could one day tell families if their children are genetically predisposed to developing the repeated behaviors and involuntary movements and vocalizations connected with OCD and tic disorders.

The blood test's development comes on the heels of findings by the same researchers that some OCD and tic disorders may be triggered by the infectious bacteria that cause strep throats, called Group A beta-hemolytic, and may be treatable with penicillin. Symptoms of OCD and tics, particularly those of Tourette syndrome, a more severe form of tic disorder, are debilitating to children, who may be ostracized by peers, teachers and others.

Susan Swedo, M.D., the study's lead author and head of behavioral pediatrics at the National Institutes of Mental Health, said there is mounting evidence that some mental illnesses are treatable biological disorders. "In psychiatry, this offers a very rare opportunity to catch a disorder early and to treat it aggressively," she said. Swedo urges doctors who examine children exhibiting an abrupt onset of OCD or tic symptoms to check the young people for strep, and if strep is present to treat it with penicillin. In some cases, OCD or tics will abate when a child is treated for strep throat, she said.

The researchers described their trait marker, D8/17, in the January issue of the American Journal of Psychiatry. Their study involves testing for the presence of D8/17 in 27 young people with OCD and tics associated with strep, nine children with Sydenham's chorea, which is a variant of rheumatic fever characterized by neurological dysfunction, and 24 healthy children. The researchers found that 85 percent of the children with strep-associated OCD and tics and 89 percent of youngsters with Sydenham's chorea were D8/17 positive compared to 17 percent of the healthy children. The typical number of D8/17 positive cells were similar in the two groups of patients and much higher compared to the healthy children.

The blood test is still a research tool that may be a few years away from regular clinical use, said Henrietta Leonard, M.D., the study's second author. But the findings suggest that a subset of children exist--those who may be genetically predisposed to involuntary actions of OCD and tics--whose sudden and acute onset is associated with strep throat. This allows clinicians to consider prevention of the abrupt appearance of OCD and tic disorders, she said.

"If we could potentially screen children at risk when they're young, we could watch the children who have this trait marker for rheumatic fever more closely and catch them right away if they begin to show OCD or tic symptoms," said Leonard. "We can also see if there is a way to prevent illness onset in the children, possibly through the use of preventative antibiotic treatments. Some kids with OCD or tic symptoms never get over how they're treated by others. Our hope is that with more research, we can change the outcome for these children." Leonard is professor and director of training for child and adolescent psychiatry in theDepartment of Psychiatry and Human Behavior, Brown University School of Medicine, and director of training in child and adolescent psychiatry at Rhode Island Hospital.

Only a small percentage of strep throat infections are associated with the appearance of OCD or tic disorders. There may be dozens of reasons why a young person develops OCD or tic symptoms. Severe OCD or tic symptoms are treated with drugs, such as Prozac or Anafranil, combined with behavior modification therapy. These treatments target control of symptoms, not elimination of causes.

Medical personnel often consider the onset of tics or other involuntary behavior in children to be the result of parental pampering and coddling, said Patricia Moore, president of the Rhode Island Chapter of the Tourette Syndrome Association, Inc. "It's time to stop telling parents that tics and other symptoms are their fault," she said.

Brown University

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