Tremor is one of the symptoms of aromatic L-amino acid decarboxylase (AADC) deficiency, a rare genetic disease caused by mutations in the DDC gene.
Such mutations cause an enzyme called AADC to not function properly. The AADC enzyme plays an important role in the production of neurotransmitters, or cell signaling molecules in the brain, like dopamine and serotonin. When the enzyme does not function properly as a result of mutation, not enough dopamine and serotonin are made.
This results in a number of symptoms, including tremor.
What is tremor?
Tremor is a shaking movement. It can affect the whole body or only specific muscles. Most often, tremor affects the hands, arms, or legs. But it also can affect the head, vocal cords, and torso. While not harmful to the patient, tremor can make it difficult or even impossible to perform work and daily life tasks.
What causes tremor?
The causes of tremor are not well understood, although it is thought to be caused by faulty communication between different areas of the brain.
In AADC deficiency, the lack of neurotransmitters can lead to faulty communication between different brain areas. Additionally, the lack of neurotransmitters during important developmental stages means that some brain areas may be poorly developed or have structural problems that also affect communication.
How is tremor treated?
There is no specific treatment for movement disorders caused by AADC deficiency. Because tremor is usually not a severe symptom, or painful, it may not require treatment.
However, physicians may prescribe medications off-label to treat this symptom. For example, medicines called beta-blockers — usually used to treat high blood pressure or cardiovascular disease — also may reduce tremor in some people.
Last updated: Oct. 3, 2019
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