Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare neuromuscular condition characterized by an imbalance in the levels of dopamine and serotonin, the neurotransmitters or messenger molecules that help the brain communicate with the rest of the body. Movement disorders are, therefore, common in people with AADC deficiency.

What are movement disorders?

There are two types of body movements — voluntary and involuntary. Voluntary movements are actions that are in an individual’s conscious control, such as throwing a ball or walking. Involuntary movements are those that are beyond a person’s conscious control, such as breathing, eye reflexes, and heartbeat.

The brain regulates muscle contraction and relaxation using neurotransmitters. Erratic communication between the brain and muscles causes movement disorders, or problems with movement. The imbalance in neurotransmitter levels seen in AADC deficiency may result in movement disorders.

Movement disorders include changes — increases and decreases — in the intensity or frequency of voluntary and involuntary movements. They usually are repetitive and painful.

Movement disorders in AADC deficiency

AADC deficiency can cause movement disorders in patients of all ages, from newborns to adults. The severity of the movement disorders varies among patients and usually worsens as the condition progresses. Common movement disorders reported in AADC deficiency are summarized below.

Dyskinesia, bradykinesia, and tremor

Dyskinesia is the increase in the frequency of a movement, such as rapid blinking or continuous clapping. Conversely, bradykinesia is slowing of the movement.

Tremor is the shaking movement of one or more body part. It most often affects the hands, but can also occur in the arms, head, vocal cords, torso, and legs.

Dystonia

Dystonia is the abnormal contraction of muscles, causing a movement to be stuck in repetitive action. The muscle spasms can range from mild to severe, and cause repetitive or twisting motions.

Oculogyric crises

Oculogyric crises are dystonia of the eye muscles that control eye movement, causing the involuntary upward movement of the eyeball. In oculogyric crises, the patient’s gaze is stuck in an upward direction. Restricted neck movement, protruding tongue, lip-smacking, anxiety, emotional outbursts such as crying, and extreme exhaustion are some of the accompanying symptoms of oculogyric crises.

Myoclonus

Myoclonus is a sudden involuntary muscle jerk. Hiccups are an example of myoclonus that occurs naturally. In AADC deficiency, involuntary muscle jerks can occur at different intensities, last a long time, and interfere with daily activities such as eating, breathing, speaking, or walking.

Treatment of movement disorders

There is no specific treatment for AADC-associated movement disorders. The healthcare team will evaluate the disorder and plan symptom management based on the patient’s needs.  The symptoms can last for hours or days. Therefore, making the patient comfortable during an episode, alleviating pain, and managing anxiety associated with the condition are the goals of the treatment.

Additional information

Movement disorders also are reported in other neurometabolic conditions, including Parkinson’s disease,  Wilson’s disease, and tyrosine hydroxylase deficiency. They also are a known side effect of antipsychotic medications.

 

Last updated: Sept. 20, 2019.

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AADC News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare providers with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Vijaya Iyer is a freelance science writer for BioNews Services. She has contributed content to their several disease-specific websites, including cystic fibrosis, multiple sclerosis, muscular dystrophy, among others. She holds a PhD in Microbiology from Kansas State University, where her research focused on molecular biology, bacterial interactions, metabolism, and animal models to study bacterial infections. Following the completion of her PhD, Dr. Iyer went on to complete three postdoctoral fellowships at Kansas State University, University of Miami and Temple University. She joined BioNews Services to utilize her scientific background and writing skills to help patients and caregivers remain abreast with important scientific breakthroughs.
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Özge has a MSc. in Molecular Genetics from the University of Leicester and a PhD in Developmental Biology from Queen Mary University of London. She worked as a Post-doctoral Research Associate at the University of Leicester for six years in the field of Behavioural Neurology before moving into science communication. She worked as the Research Communication Officer at a London based charity for almost two years.
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Vijaya Iyer is a freelance science writer for BioNews Services. She has contributed content to their several disease-specific websites, including cystic fibrosis, multiple sclerosis, muscular dystrophy, among others. She holds a PhD in Microbiology from Kansas State University, where her research focused on molecular biology, bacterial interactions, metabolism, and animal models to study bacterial infections. Following the completion of her PhD, Dr. Iyer went on to complete three postdoctoral fellowships at Kansas State University, University of Miami and Temple University. She joined BioNews Services to utilize her scientific background and writing skills to help patients and caregivers remain abreast with important scientific breakthroughs.
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