AADC deficiency FAQs

Here are some frequently asked questions (FAQs) about aromatic L-amino acid decarboxylase (AADC) deficiency.

What is AADC deficiency?

AADC deficiency is a rare, inherited, genetic condition. It affects a child’s nervous system and prevents normal childhood development, including movement, eating, speech and mental ability.

Learn more about what causes AADC deficiency and the common signs and symptoms of the condition by watching this short animation ‘What is AADC deficiency?’

What are the signs and symptoms of AADC deficiency?

Symptoms of AADC deficiency usually appear in early infancy. AADC deficiency can cause a range of different symptoms, including floppiness (also known as low muscle tone or hypotonia), delays in development, involuntary eye movements (also known as oculogyric crises), and multiple symptoms associated with bodily functions, such as excessive sweating, runny nose or droopy eyelids. The signs and symptoms, and severity, will vary from person to person. Find out more about the signs and symptoms of AADC deficiency.

If your child has floppiness (low muscle tone) that is unexplained and not improving, there are other symptoms that you can look for to help you decide if you should talk with your child’s doctor about AADC deficiency. Sometimes, other more common conditions can have symptoms that look the same as AADC deficiency, such as cerebral palsy or epilepsy.

For more information on the signs and symptoms of AADC deficiency, listen to our RareTalks podcast episode ‘What is AADC deficiency?’

What causes AADC deficiency?

AADC deficiency is a genetic disorder. Genetic disorders are caused by a change in a person’s DNA. AADC deficiency is caused by a change, known as a mutation, in a gene called dopa decarboxylase (also known as DDC). The DDC gene is needed to make an enzyme called aromatic L-amino acid decarboxylase (also known as AADC). Mutations in the DDC gene mean that the body can only produce a small amount of the AADC enzyme or doesn’t make any at all. In turn, this results in the signs and symptoms associated with AADC deficiency.

Find out more about what is a genetic disorder and what causes AADC deficiency.

What does AADC do?

AADC is an enzyme that is responsible for the production of chemical messengers, called neurotransmitters, such as dopamine and serotonin. These chemicals are used to send messages between the cells in the nervous system.

In children with AADC deficiency, the lack or deficiency of AADC affects the body’s production of the chemical messengers, serotonin and dopamine. Without a functional messaging system, important processes in the body are impacted, leading to symptoms that limit the activities of daily life.

Find out more about what is a genetic disorder and what causes AADC deficiency.

What are neurotransmitters?

Neurotransmitters are chemical messengers that are used to send messages between nerve cells in the body. These chemical messages control many of the body’s functions, such as moving, learning, behaviour, and managing emotions and pain.

Discover more about neurotransmitters and their role in AADC deficiency.

What role does the putamen play in AADC deficiency?

The putamen is a major site of AADC enzyme activity in the brain. Since AADC is responsible for making dopamine, a reduction in AADC enzyme activity reduces the amount of dopamine in the putamen.

With less dopamine, children with AADC deficiency display symptoms such as movement difficulties, behavioural problems and development delay.

Discover more about the putamen or learn more about the symptoms of AADC deficiency.

If AADC deficiency is a genetic disorder, can it be inherited from a parent?

Yes, AADC deficiency is inherited from parents.

Our genes come from our parents, and we get one copy of each gene from each parent. Each copy may be a healthy working copy or a copy that does not work as it is supposed to (an altered or mutated copy). For a child to have AADC deficiency, both parents must pass down an altered copy of the DDC gene, meaning the child has two altered copies in total. Because both copies of the DDC gene must be altered for a child to have AADC deficiency, it is known as an autosomal recessive disorder.

A child with one copy of the mutation is unlikely to develop any symptoms of AADC deficiency and is called a carrier of the disease.

Find out more about the genetic causes of AADC deficiency or listen to our RareTalks podcast episode ‘What is AADC deficiency?’

How is AADC deficiency diagnosed?

If your child has weak muscle tone (is floppy) and delayed development, your doctor may perform a range of tests that are not specific for AADC deficiency, but can help identify problems in the brain, such as magnetic resonance imaging (MRI) and computed tomography (CT) scans, or an electroencephalogram (EEG). If these tests do not seem to suggest a specific diagnosis, the doctor may do additional tests.

Core tests to diagnose AADC deficiency include a lumbar puncture for cerebrospinal fluid (CSF) in order to do a neurotransmitter metabolite panel, a blood test for plasma AADC enzyme activity, and genetic testing. Your child’s doctor may recommend genetic testing to look for a mutation or change in the DDC gene.

Your child’s doctor may also order other tests that will be helpful in diagnosing your child, including blood and urine tests.

If you think your child should be tested for AADC deficiency, talk to your doctor.

Learn more about the red flag symptoms that suggest AADC deficiency, and the steps required to confirm a suspected diagnosis, in this short animation ‘How to diagnose AADC deficiency’.

What types of doctors can diagnose AADC deficiency?

There are several types of doctor that can diagnose AADC deficiency: a Paediatric Neurologist, a Movement Disorder Specialist and a Clinical Geneticist.

Download and fill out a symptom questionnaire to take to your appointment with your child’s doctor to help you explain what your child is experiencing.

How can I prepare for an appointment with my child’s doctor?

You may feel overwhelmed with questions if your child has symptoms, but you do not yet have a diagnosis. Or if you have a diagnosis, you may have some questions about what happens next.

You may find it helpful to prepare a list of questions as you think of them in the run-up to your appointment and bring this list with you. You can also make notes in your appointment, so that you don’t forget what your doctor has said.

Keep any information that you are given in the same place, so that you can refer back to it if you need to – or use this information to help answer questions in the future.

If you think it would be useful, don’t be afraid to ask your doctor for copies of written notes or information so that you can refer to it or research later.

Download and fill out a symptom questionnaire to take to your appointment with your child’s doctor to help you explain what your child is experiencing.

Are there any conditions with symptoms that are similar to AADC deficiency?

Yes, many of the symptoms of AADC deficiency can be similar to other disorders, making it difficult to diagnose.

AADC deficiency is rare, and many of its symptoms may overlap with those of other more common disorders such as epilepsy/seizures, cerebral palsy, mitochondrial disease and neuromuscular weakness.

Although symptoms are often seen when a child is still an infant, a diagnosis may take a long time, and you might need to have your child seen by a number of specialists.

Learn more about other conditions with similar symptoms to AADC deficiency and listen to one family’s journey to getting the right diagnosis.

My child has just been diagnosed with AADC deficiency; what do I do now?

Your child’s doctor may discuss treatments that may help improve some of your child’s symptoms, and assemble a team of professionals to help manage your child’s symptoms and quality of life. Members of your team may include a Paediatrician or General Practitioner, a Paediatric Neurologist, a Movement Disorder Specialist, a Clinical Geneticist, a Gastroenterologist, a Physiotherapist, an Occupational Therapist, a Speech Therapist and a Developmental Paediatrician.

Ask your child’s doctor about medications and physical, occupational, and speech therapy, and about other treatments that may help improve some of your child’s symptoms and quality of life.

Listen to Dr Roberta Scalise provide some helpful guidance on the next steps following a diagnosis of AADC deficiency in our RareTalks podcast episode ‘What is AADC deficiency?’

How does having a child with AADC deficiency impact caregivers?

The needs of a child with AADC deficiency can have a significant impact on the lives of caregivers. Children with AADC deficiency may need round-the-clock care, and caregivers have reported spending an average of 13 hours per day looking after the practical and emotional needs of their child.

Find out more about living with AADC or discover the quality of life with AADC deficiency.

Are there any tips for carers of individuals with AADC deficiency?

There are a variety of websites and support groups that can help caregivers find information and resources.

Take a look at our resource library, where you will be able to watch videos from families who are living with AADC deficiency, listen to the ‘About AADC podcasts series’ and download a copy of the Caregiver Brochure that provides more information to those who care for someone with AADC deficiency.