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Amino acid: a type of compound that is the building block of proteins.

Aromatic L-amino acid decarboxylase (AADC): an enzyme which helps to produce some of the neurotransmitter molecules used to send messages between nerve cells.

Akinesia: the loss of the ability to move your muscles on your own.

Autonomic nervous system: the part of the nervous system which controls normal bodily functions without conscious control. Problems with the autonomic nervous system can lead to symptoms such as drooling, excessive sweating, a runny nose and problems with digestion.


By-product: a substance that is created in the process of making something else.


Caregiver: someone who regularly looks after and provides care or assistance to someone, such as a child, an elderly person, or someone who is sick or disabled.

Cerebral palsy: a disability resulting from damage to the brain before, during, or shortly after birth that causes issues with body movement, muscle tone, speech disturbances, and/or other medical issues.

Cerebrospinal fluid (CSF): the fluid surrounding the brain and spinal cord.

Chorea: involuntary, irregular and unpredictable muscle movements which can make a baby look restless or fidgety

Clinical Geneticist: a doctor who is trained to help identify and study genetic disorders.

Computed tomography (CT): a scan that uses a series of X-ray images taken from different angles around the body and uses computer processing to create a cross-sectional image of the inside of the body.


Deficiency: a lack or shortage of something.

Developmental delay: when a child does not meet normal milestones for development, such as sitting without support, crawling and walking.

Diurnal variation: where symptoms change over the course of a day. Often, they become worse or more noticeable later in the day and improve with sleep.

Dopa decarboxylase (DDC) gene: a gene that provides instructions for making the enzyme aromatic L-amino acid decarboxylase (AADC), which is important in the brain and nervous system.

Dyskinesia: involuntary and erratic movements of muscles in the face, arms, legs or trunk which might look like tics or chorea.

Dystonia: involuntary muscle contractions that cause slow, repetitive movements or abnormal postures.


Electroencephalogram (EEG): a test that looks at abnormalities in the brain by attaching small metal electrodes to the scalp in order to detect tiny electrical charges from brain activity.

Enzyme: a substance that helps to bring about, speed up, or regulate chemical reactions.

Epilepsy: a chronic disorder that causes sudden episodes in which the patient may lose consciousness, have his/her senses disrupted, shake uncontrollably, and/or show other symptoms (for example, seizures or fits); often caused by abnormal electrical activity in the brain.


Flailing: waving or swinging wildly.


Gastroenterologist: a medical professional who specialises in identifying and treating disorders of the stomach and intestines.

General Practitioner: a medical professional who is trained to provide healthcare to patients of any gender or age.

Genetic: relating to or determined by genes; something that is passed down through families and considered inherited.

Genetic testing: a study of DNA to find differences, abnormalities, or changes that could cause disorders or to determine if a person has or will develop a certain disease.


Hypotonia: low muscle tone, often involving reduced muscle strength.


Involuntary: done without conscious control.


Lumbar puncture: a medical procedure in which fluid from the spine is removed with a needle; often done for diagnostic testing. Also called a spinal tap.


Magnetic resonance imaging (MRI): a test that uses a magnetic field and radio waves to create detailed images of the body’s organs and structures.

Metabolite: any substance that is made during the changing of one chemical compound into another.

Mitochondrial disorder: a condition causing problems with the way mitochondria work. Mitochondria are the structures in cells which produce energy.

Movement Disorder Specialist: a healthcare professional who has special training in disorders that affect someone’s ability to move, such as Parkinson’s disease, or that involve low muscle tone (hypotonia) or tremors.

Muscle spasm: an uncontrolled tightening of a muscle that can cause a great deal of pain.

Muscle tone: the amount of tension or resistance in a muscle at rest or in response to stretching.

Mutation: a change that happens in a gene.

Myoclonus: an involuntary sudden jerk, twitch or spasm of a muscle.


Nervous system: an organ system of the body made up of the brain, spinal cord, and nerves.

Neurological: relating to the makeup, functions, and disorders of the nervous system.

Neuromuscular: relating to nerves and muscles.

Neurotransmitter: a chemical substance that works as a messenger to send signals from one nerve cell to another.


Occupational Therapist: a healthcare professional who works to help mentally, physically, and developmentally disabled patients improve their ability to participate in everyday activities.

Oculogyric crises: periods of involuntary eye movements during which the eyes suddenly roll upward involuntarily; can last anywhere from a few seconds to hours, and can happen several times a day or several times a week.


Paediatrician: a medical professional who specialises in the development, care, and treatment of children and their diseases.

Paediatric Neurologist: a medical professional who focuses on studying and treating diseases and conditions that affect the nervous system of children.

Physiotherapist: a trained healthcare professional who helps patients reduce pain and strengthen muscles to improve mobility.

Plasma: the colourless fluid part of blood.

Precursor: a substance from which another substance is created.

Ptosis: drooping or falling of the upper eyelid.


Reflux: to flow backward in the body, such as from the stomach.


Seizure: a sudden attack, spasm, or convulsion, as in epilepsy or another disorder.

Spasticity: stiffness caused by prolonged contraction of muscles.

Speech Therapist: a healthcare professional who specialises in the treatment of speech and communication disorders.

Symptom: an indication of a disease or a change in a condition that the patient notices.

GL-AADC-1078 | February 2022

Welcome to About AADC

A website for parents and caregivers of children with AADC deficiency, and members of the public interested in the condition. This website has been provided by PTC Therapeutics.

This educational website provides information to support awareness of a rare neurotransmitter disorder called aromatic L-amino acid decarboxylase (AADC) deficiency.