Dystonia may be an inherited condition caused by genetic mutations. It can also result from exposure to certain drugs, birth injuries, strokes, or as a symptom of other neurological disorders. For many patients, however, the cause remains unknown. There are two main categories of causes of dystonia: primary and secondary (or non-primary).
Primary dystonia is a condition in which dystonia is the only clinical feature. There is no evidence of cell death or a known cause. It is also known as idiopathic torsion dystonia. The primary dystonias are often inherited from a parent or an apparent cause is not found. Researchers over the past twenty years have identified mutations in two genes (DYT1 and DYT6) as responsible for many cases of primary dystonia. Most genetic forms of dystonia start with symptoms in childhood or adolescence. Commercial tests are available to determine if these genes are affected in individuals.
In non-primary or secondary dystonia, an acquired or exogenous cause is identified. This can be a prior stroke, a birth injury or exposure to certain drugs. Secondary dystonia may also represent one symptom of other neurological disorders, such as Parkinson’s disease.
Some genetic causes include:
- - Myoclonus Dystonia
- - Dopa-responsive Dystonia
- - Rapid-onset Dystonia Parkinsonism
- - Wilson’s Disease
- - Huntington’s Disease
- - Spinocerebellar Ataxias
- - Methymalonic Aciduria
- - Parkinson’s disease caused by Parkin mutations
Acquired causes include:
- - Exposure to drugs such as certain antipsychotic and anti-nausea medications (also called tardive dystonia)
- - Multiple sclerosis
- - Past history of stroke, birth injury, infections, or trauma