The prevalence of early-onset torsion dystonia varies depending upon the population. Ashkenazi Jews have a high prevalence of the disorder, around 1 in 10,000, due to a mutation in the DYT1 gene in a common ancestor hundreds of years ago. That mutation, called a founder mutation, has been passed down from the original carrier of the gene to subsequent generations. Dr. Breakefield's team believes that the same mutation in the DYT1 gene appeared independently in several other ethnic populations throughout history, and is possibly one of only a few mutations that result in early-onset torsion dystonia. Researchers believe that dystonia may be caused by a breakdown of the dopamine system in the basal ganglia, a collection of structures in the brain that control movement.
Dopamine is a neurotransmitter that regulates neuronal communication within the basal ganglia.
A malfunctioning dopamine system in the basal ganglia is responsible for many movement disorders, including Parkinson's disease. Researchers have mapped a total of seven genes causing dystonia and sequenced two that code for proteins involved in dopamine systems. Dopamine therapy seems to work for some kinds of dystonia, but is not effective for children with generalized torsion dystonia. The next task for Drs. Breakefield and Ozelius is to clarify the function of torsinA. Working in collaboration with other members of the team they will develop an animal model for early-onset torsion dystonia.