Blood Test May Yield Marker For Childhood Behavioral Disorders Say University Of Florida Researchers

GAINESVILLE, Fla.---A telltale protein believed to be linked to certain formsof obsessive-compulsive disorder (OCD) and Tourette's syndrome, a mysteriousand 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 beused to identify patients who are genetically predisposed to developing thesedisruptive disorders and could lead to improved treatments or even ways toprevent the illnesses.

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

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

More than 5 million Americans suffer from OCD, which is characterized by apreoccupation with unwanted fears, thoughts and images, such as fear ofcontamination. These obsessions lead to compulsive behaviors--repeatedlywashing hands, wiping off door handles, for example.

Tourette's syndrome affects more than 200,000 people nationwide. Onceconsidered an emotional illness, the neurological disease is oftencharacterized by involuntary muscular tics -- such as eye twitching, headjerking 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 Marchissue of the American Journal of Psychiatry, strengthens evidence thatTourette's and some forms of OCD are related -- physiologically and possiblygenetically.

The same antigen marker, in fact, also is known to be present in excessiveamounts 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 complicationof streptococcus infection, or strep throat.

"Sydenham's chorea may serve as a medical model for some forms ofobsessive-compulsive disorder and Tourette's syndrome," said UF pediatricpsychiatrist Tanya Murphy, lead author of the recent journal report. "Ourfindings suggest that this antigen may serve as a marker for susceptibility tosome forms of childhood-onset obsessive-compulsive disorder and Tourette'ssyndrome, as well as Sydenham's chorea and rheumatic fever."

"It is too early to know whether some cases of childhood-onset OCD andTourette's may be related to strep throat," Murphy added. "It may becoincidental or it may be directly related that these illnesses all share thesame biological marker. These questions give us a direction for futurestudies."

Previous research indicates these illnesses may share more than a commonmarker. Evidence also shows Sydenham's chorea and OCD involve chemicaldisruptions in the brain's basal ganglia -- clusters of nerve cells at thebase of the brain that help regulate body movements. The disruptions arethought to occur when antibodies directed against the streptococcus infectionreact with these nerve cells and other brain tissue, causing movementdisorders and behavioral disturbances.

While Murphy cautions that more research is required before the D8/17 antigencan be conclusively declared as a marker for children at risk of OCD andTourette's, she does offer some advice to parents of children with strepthroat.

"If a child had a strep throat infection and within two or three monthsexhibits significant behavioral changes," Murphy said, "the parents shouldconsider that this may be a complication of strep throat and seek furthermedical evaluation of their child."

Murphy's co-researcher Dr. Wayne Goodman, professor and associate chairman ofpsychiatry at the UF Health Science Center's Jacksonville campus, recentlyreceived a three-year federal grant of $887,000 to further study the interplaybetween genetics, infection and autoimmune factors in the biology of childhoodOCD and Tourette's.

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

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