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Genes R US — What you need to know about Tourette syndrome

Genes R US — What you need to know about Tourette syndrome

Posted: Wednesday, June 13, 2012 5:00 pm

Tourette syndrome (TS) is a childhood-onset neurological disorder characterized by multiple tics. The most common tic is eye-blinking, which is a motor tic. Coprolalia is a vocal tic where socially unacceptable words or phrases are blurted out. This is the tic most people associate with TS, but coprolalia is the least common tic of all.
Tics can include behaviours like shoulder shrugging, coughing, clearing one’s throat, turning the lights off and on, facial grimacing, repeated words and phrases, jumping, snapping fingers-basically any behaviour that is done repeatedly, excessively, and irresistibly. Tics can vary from mild to severe
Tension builds up until the person with TS acts out the tic. With maturity, an individual becomes more aware of the social implications of his tics; and with great effort, he may be able to suppress the tic until a more private location is available. But invariably the tic will find its way “out.” Stress makes tics much, much worse.
About 200,000 people are estimated to have TS in this country, but the overall incidence is very likely underestimated as many people have the syndrome without the diagnosis. TS affects more males than females, which is similar to the gender bias for those on the autistic spectrum. However, TS is distinct from autism.
The diagnosis of TS is usually made between the ages of six and eighteen years of age and only in the presence of multiple motor tics and at least one vocal tic. To receive a formal diagnosis, tics do not need to present simultaneously, but they must have been present for nine months out of a year, and they must cause some level of social impairment.
A wonderful documentary entitled, Different Is the New Normal–Living a Life with Tourette’s, puts a face on TS. The handsome face is that of Ariel Small, a male teenager blessed with a super Mom and also “blessed” with TS. 
In the film Ariel shares how he was diagnosed with TS at the age of six. By middle school, he had learned to mask his tics by making jokes out of them to become the class clown. This helped him gain friendship with and acceptance by his peers. But this same coping mechanism earned him the label of behavioral problem in his school.
In as many as fifty percent of TS individuals, other concurrent neurological disorders are often identified such as obsessive compulsive disorder (OCD), attention deficient hyperactivity disorder (ADHD), and learning difficulties. TS implies
no particular intellectual deficient as the range of intelligence is identical to those persons without TS. 
Three years before the first human genome was sequenced, there was great optimism about finding the genetic cause of TS. A decade later, despite an intensive search for causative genes, we know very little about the genetics of TS except that it is must involve multiple genes.
For sure, TS has a hereditary component-but it has a complex form of inheritance. Identical twins studies demonstrate that there is an environmental factor-genes alone are not enough. One-quarter to one-half of identical twins are free from Tourette’s while the other has the syndrome.
Other than one SNP (a single point DNA variation) that is located in the gene TPH2, little is known genetically about TS. TPH2 controls serotonin production, an important neurotransmitter. However, decreased concentrations of serotonin have been found in the cerebrospinal fluid of Tourette’s patients.
Imaging and post-mortem studies on brains of TS patients suggest a role for overactive dopamine receptors and involvement of the brain’s basal ganglia. (Dopamine is critical neurotransmitter, as is serotonin.) Medications, such as those inhibiting dopamine, can be helpful for some patients with Tourette’s. But finding a medical doctor who specializes in the treatment of TS can be tricky. 
For you the reader, if you work in the educational system or your family is impacted by Tourette’s, it is important to realize that these tics are involuntary and unintentional. With much effort, time (especially time), and sometimes medication, it is possible for individuals with TS to gain some measure of control over the when, where, and the how of their tics.
I suspect we will need to wait for very affordable full-genome sequencing studies to unravel the genetics of Tourette’s.
Nancy@ NancyMillerLatimer.com has worked in scientific research and development for 27 years. She blogs at NeuronalBeauty.BlogSpot.com Published in The Messenger 6.13.12

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