Blood Test May Yield Marker For Childhood Behavioral Disorders

May 1, 1997

GAINESVILLE — A telltale protein believed to be linked to certain forms of obsessive-compulsive disorder (OCD) and Tourette’s syndrome, a mysterious and humiliating nervous disorder, may be detected through a simple blood test, according to a recent University of Florida study.

Researchers at UF’s College of Medicine say such a screening test could be used to identify patients who are genetically predisposed to developing these disruptive disorders and could lead to improved treatments or even ways to prevent the illnesses.

In the UF study, blood analyses revealed that all 31 patients with either childhood-onset OCD or Tourette’s syndrome had abnormally high levels of a specific protein in crucial blood cells of the immune defense system. Among a control group of 21 healthy participants, only one displayed evidence of the marker protein, known as antigen D8/17.

Antigens are proteins that lock onto the surfaces of invading viruses and mark them for destruction by the immune system.

More than 5 million Americans suffer from OCD, which is characterized by a preoccupation with unwanted fears, thoughts and images, such as fear of contamination. These obsessions lead to compulsive behaviors–repeatedly washing hands, wiping off door handles, for example.

Tourette’s syndrome affects more than 200,000 people nationwide. Once considered an emotional illness, the neurological disease is often characterized by involuntary muscular tics — such as eye twitching, head jerking and other facial grimaces — along with socially awkward snorting, throat noises and involuntary outbursts of obscenities.

The common biological marker revealed in the UF study, reported in the March issue of the American Journal of Psychiatry, strengthens evidence that Tourette’s and some forms of OCD are related — physiologically and possibly genetically.

The same antigen marker, in fact, also is known to be present in excessive amounts in people with another movement disorder called Sydenham’s chorea, which produces symptoms similar to those of OCD or Tourette’s syndrome. Sydenham’s chorea sometimes accompanies rheumatic fever, a rare complication of streptococcus infection, or strep throat.

“Sydenham’s chorea may serve as a medical model for some forms of obsessive-compulsive disorder and Tourette’s syndrome,” said UF pediatric psychiatrist Tanya Murphy, lead author of the recent journal report. “Our findings suggest that this antigen may serve as a marker for susceptibility to some forms of childhood-onset obsessive-compulsive disorder and Tourette’s syndrome, as well as Sydenham’s chorea and rheumatic fever.

“It is too early to know whether some cases of childhood-onset OCD and Tourette’s may be related to strep throat,” Murphy added. “It may be coincidental or it may be directly related that these illnesses all share the same biological marker. These questions give us a direction for future studies.”

Previous research indicates these illnesses may share more than a common marker. Evidence also shows Sydenham’s chorea and OCD involve chemical disruptions in the brain’s basal ganglia — clusters of nerve cells at the base of the brain that help regulate body movements. The disruptions are thought to occur when antibodies directed against the streptococcus infection react with these nerve cells and other brain tissue, causing movement disorders and behavioral disturbances.

While Murphy cautions that more research is required before the D8/17 antigen can be conclusively declared as a marker for children at risk of OCD and Tourette’s, she does offer some advice to parents of children with strep throat.

“If a child had a strep throat infection and within two or three months exhibits significant behavioral changes,” Murphy said, “the parents should consider that this may be a complication of strep throat and seek further medical evaluation of their child.”

Murphy’s co-researcher Dr. Wayne Goodman, professor and associate chairman of psychiatry at the UF Health Science Center’s Jacksonville campus, recently received a three-year federal grant of $887,000 to further study the interplay between genetics, infection and autoimmune factors in the biology of childhood OCD and Tourette’s.

Their collaborators include Dr. Ralph Williams, an eminent scholar in rheumatoid arthritis research who helped develop the D8/17 screening test, and Dr. Elia Ayoub, a distinguished service professor in pediatric infectious diseases.