Giles De La Tourette Syndrome, named after the French neurologist who first described it, is a severely debilitating disorder, characterized by repetitive, rapid, and stereotyped muscular movements (tics). Both motor tics (blinking, pouting, eye rolling, shoulder shrugs, head jerks, facial grimacing, head nodding) and to a lesser extent, vocal or phonic tics (coughing sniffing, throat clearing) can be seen in the patients, although they may not present themselves at the same time. Over half of the patients develop complex movements which include jumping, kicking, stamping, and hitting. An added complication is the presence of coprolalia in about 10% of the patients, which manifests itself in the form of usage of socially inappropriate words or phrases in public. Unlike the presence of tics in other diseases, in GTS, the tics are "compelling" rather than "involuntary". In addition, patients also show a higher chance of being affected with Attention Deficit/Hyperactivity Disorder (ADHD), Obsessive Compulsive Disorder (OCD), learning disabilities like Dyslexia, and/or sleep disorders.
Tourette syndrome has historically been described as a rare disorder, with about 5 to 10 people in 10,000 having the condition. However, multiple studies published since 2000 demonstrate that the prevalence is much higher than previously thought, and that Tourette syndrome can no longer be considered rare. Contemporary prevalence estimates range from 1 to 3 per 1,000 to 10 per 1,000. The disease affects people of all ethnicities, and is three to four times more common in males than in females.
Symptoms of the disease usually appear before the age of 21 years. Diagnostic criteria include presence of motor and phonic tics, age of onset before 21 years, and periodic changes in the severity, frequency and number of the bouts. Treatment of the syndrome focuses more on controlling the tics, and relieving tic-related discomfort and social embarrassment. For less severe cases, medication is avoided, since most medications lead to side effects such as excessive fatigue, weight gain, and parkinsonian symptoms among others. However, for co-morbid cases, and more severe cases of GTS, medication may be prescribed.
The molecular genetics of this disorder are not very clear. However, it seems likely that the disease manifests itself due to abnormal metabolism of dopamine and serotonin neurotransmitters. A study involving the presence of GTS in large family pedigrees proves the genetic nature of the disease. An autosomal dominant mode of inheritance has been attributed to this disease. Recent studies have implicated the SLITRK1 (SLIT and NTRK-Like Family Member 1) gene to be the defective gene in at least some of the cases of GTS. Mutations in HDC (Histidine Decarboxylase) gene has also been identified to be causative in a large 2-generation family with GTS. Interestingly, the disease shows differential penetrance in males and females; males having a 99% chance of displaying the symptoms, whereas females have only a 70% chance.