Although most people diagnosed with Tourette's syndrome go on to lead productive lives, facial tics and involuntary movement can make everyday life difficult and can create a stigma around that person. A study out of the Yale University School of Medicine found that Tourette's syndrome may be caused by a rare genetic mutation that affects histamine production in the brain.
“These findings give us a new window into what’s going on in the brain in people with Tourette,” said Christopher Pittenger, associate professor at the Yale Child Study Center. “That’s likely to lead us to new treatments.”
According to the National Institute of Neurological Disorders and Stroke, Tourette's syndrome is a neurological disorder characterized by involuntary movements known as tics. In order to be diagnosed with Tourette’s, a person must suffer from both motor tics such as blinking and shrugging the shoulders and vocal tics such as yelling out or barking. People with the condition also experience tics for at least a year, start tics before they turn 18, and display symptoms that are not caused by medication or another existing illness.
Approximately 200,000 people in the United States are currently affected by the most severe form of Tourette's syndrome. One out of every 100 Americans shows signs of milder symptoms including the occasional motor or vocal tic. Tourette’s symptoms tend to be worse during teenage years and start to alleviate during late teen years and early adulthood. Boys are three to four times more likely to be diagnosed with Tourette's syndrome.
After observing a family with nine members suffering from Tourette's syndrome, the research team from Yale decided to uncover the hereditary link. Pittenger and his colleagues from the university identified a gene that disrupts histamine production, known as HDC. Histamine is an important signaling molecule in the brain that also affects allergy symptoms. Mice that were given the HDC mutation also began to experience symptoms consistent with Tourette’s.
“We know that Tourette is about 90 percent genetic,” Pittenger added. “But it’s been incredibly hard to find any genetic abnormalities that cause the syndrome. We have proven that this gene really is the cause of Tourette in this family and also looked at some of its downstream effects.”
Next, researchers hope to test the effects of anti-histamine medication on patients diagnosed with Tourette’s syndrome. Drugs that target histamine receptors in the brain were developed to treat conditions such as allergies, schizophrenia, and ADHD. Antipsychotic medications, which block the brain’s production of dopamine, are currently prescribed to people with Tourette’s syndrome.
Source: Baldan L, Williams K, Pittenger C. Histidine Decarboxylase Deficiency Causes Tourette Syndrome: Parallel Findings in Humans and Mice. Neuron. 2013.