Last updated: 2003-09-11
The tragedy of dystonia, a disease affecting movement control, may be best described through the brief case history of a young girl.
Her early development was quite normal, but at age six she complained of difficulty walking. Medical evaluation first revealed no explanation, and the problem was mistakenly considered psychological. However, her torsion spasms progressed and by age 10 she could hardly walk. At age 11, the dystonia was generalized, her limbs became rigid and contracted, and she had to rely on a wheelchair for mobility. By age 12, she required help for all her daily living activities; she could not feed or dress herself or get in or out of bed unassisted. However, her voice and her mind remained normal.
The earliest description of familial dystonia may have been in 1907 by a psychiatrist-in-training who reported on two brothers and a sister who were hospitalized for "hysterical" torsion spasms. One brother committed suicide in the institution, the sister eventually died of the disease, but the second brother was discharged after several years and later married and had an affected son and daughter.
Life expectancy for individuals with dystonia is usually normal. Some medications have been found to be useful in a proportion of patients, particularly children. Injections of certain drugs into contracting muscles in order to weaken them can be helpful in those who have dystonia limited to only one or two parts of the body. Brain surgery may be useful in some cases of severe intractable dystonia.
One inherited form of dystonia is more common in Ashkenazi Jews. This form of dystonia is inherited in an autosomal dominant manner. As with the girl described above, the disease generally appears between the ages of six and sixteen years, and progresses fairly rapidly. The sustained, twisting spasms may be limited to one limb at first but often spread to other limbs and the midsection. The mind is not affected and patients usually are intelligent and mature.
The disease can affect non-Jewish families as well, but at a much lower frequency. In 1997 the gene reponsible for dystonia in the Ashkenazi Jewish population (as well as in seven non-Jewish families) was identified on chromosome 9. This gene has been excluded as the cause of dystonia from at least five non-Jewish patients, indicating the existence of at least one other gene causing dystonia in these patients. A disorder mimicking dystonia may also occur as a result of environmental causes, such as drug reaction, encephalitis (inflammation of the brain), or trauma to the head.
The children of an individual affected with dystonia due to mutations in the gene on chromosome 9 have a 50% chance of inheriting the gene mutation which causes the disease, but symptoms of dystonia occur in only 30% of individuals who inherit the dystonia gene mutation. Thus, although approximately 1 in 900 Ashkenazi Jews carries the dystonia gene mutation, only 1 in every 3,000 Ashkenazi Jewish individuals develops symptoms. Because symptoms of the disease are not always expressed, the disorder may occur in individuals with no previous family history.
One mutation in the gene appears to be the cause of torsion dystonia in almost all affected Ashkenazi Jews, and genealogical research has shown that this dystonia gene mutation in the Ashkenazi Jewish population came from a single mutation about 400 years ago. Genetic testing, including prenatal diagnosis, is therefore now available for Ashkenazi Jewish individuals.