Aromatic L-Amino Acid Decarboxylase Deficiency
Aromatic L-Amino Acid Decarboxylase Deficiency
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Child Neurology Foundation Disorder Directory AADC Deficiency

Authors: Mekka R. Garcia, MD, NYU Grossman School of Medicine; Alison L. Christy, MD, PhD, Providence Pediatric Neurology at St. Vincent Medical Center – Portland, Oregon 

Reviewed: August 2021 


Aromatic L-amino acid decarboxylase deficiency (AADC deficiency) is a rare genetic disorder. It affects the brain. It causes problems with: 

  • Walking 
  • Eating 
  • Behavior 
  • Sleep  

This is a rare disorder. Therefore, a thorough history, clinical examination, blood tests, and imaging are all key to diagnosis. There is no cure. However, supportive care is available.  

Understanding AADC Deficiency 

An enzyme is a protein that aids chemical reactions in the body. Aromatic L-amino acid decarboxylase (AADC) is an enzyme that helps produce neurotransmitters. These are chemical messengers. They help neurons, cells in the nervous system, communicate with each other.  


Disorder Overview


AADC deficiency occurs when there is an abnormality in a gene called DDC. This gene produces AADC. When the DDC gene is different, AADC may not work as usual. There may be a decrease in AADC activity. This makes it harder for neurons to communicate.

Children with this disorder look normal at birth. However, they usually develop signs and symptoms of the deficiency within the first year of life. 



Signs and symptoms of AADC deficiency often begin shortly after birth.

They may include: 


Also known as floppiness.

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Oculogyric crises

An involuntary and sustained movement of the eyes. Usually an upward movement of the eyes. 

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Delayed development

An inability to: 

  • Lift the head 
  • Crawl 
  • Sit 
  • Walk 
  • Say words.  
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Unusual movements

These can consist of: 

  • Twisting 
  • Flailing 
  • Jerking 
  • Tremors 
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Autonomic nervous system dysfunction

The autonomic nervous system regulates many functions of the body. It regulates heart rate, blood pressure, blood sugar, and temperature. Symptoms of dysfunction include: 

  • Excessive sweating 
  • Droopy eyelids 
  • Temperature instability 
  • Low blood pressures 
  • Nasal congestion 
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Seizures are a burst of electrical activity in the brain. They can cause the body to behave abnormally. 

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Behavioral problems

These can include: 

  • Irritability 
  • Excessive crying. 
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Sleep disturbances

These can include: 

  • Abnormal sleep cycles 
  • Trouble falling asleep 
  • Trouble staying asleep. 
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Gastrointestinal problems

These can include: 

  • Diarrhea 
  • Constipation 
  • Reflux 
  • Feeding difficulties 
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A diagnosis of AADC deficiency requires: 

  • A complete medical history of birth, early life, and development 
  • A thorough physical examination in the clinic 
  • Blood testing 
  • Imaging of the nervous system 


AADC deficiency occurs when there is an abnormal difference in a certain gene in the body. The gene is called the dopa decarboxylase gene or DDC gene. An abnormal DDC gene produces abnormal AADC enzymes. AADC enzymes are important for the formation of neurotransmitters. AADC deficiency affects two neurotransmitters in particular—dopamine and serotonin.

These are responsible for: 

  • Motor control 
  • Behavior 
  • Sleep 
  • The autonomic nervous system 

Disease Inheritance 

AADC deficiency is an autosomal recessive disorder. This means that a child with this disorder must inherit one abnormal gene from the mother and one abnormal gene from the father.  

If a child inherits one abnormal gene and one normal gene: 

  • They will usually not have symptoms 
  • They will instead be called a “carrier” of the disorder 

If both parents carry the abnormal gene: 

  • The risk of a child having the disorder is 25%, or 1 in 4, with each pregnancy 

The risk of inheriting this disorder is the same for males and females. It is more common in people of Asian descent.  

Spinal Muscular Atrophy 1


There are a few ways to learn more about a child’s AADC deficiency. 

Genetic Testing

A blood or saliva test can identify differences in the DDC gene. 

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Plasma AADC enzyme activity testing

A blood test can measure the activity of the enzyme. 

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Electroencephalogram (EEG)

A test of the brain’s electrical activity can be helpful in looking for seizures. 

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Magnetic resonance imaging (MRI)

A picture of the brain can look for signs of injury or other abnormalitiesFindings can sometimes help rule out AADC deficiency.

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Lumbar puncture

A sample of fluid can be removed from around the brain and spinal cord. This may be used to measure levels of certain neurotransmitters. 

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There is no cure for AADC deficiency. Therefore, therapies are aimed at symptomatic and supportive care. 

Medications used for this disorder include: 

Nasal decongestants

Can help with nasal congestion.  

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Can block some neurotransmitters. They can be used to control motor symptoms. 

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MAO-B inhibitors

Can increase the quantity of neurotransmitters in the brain.  

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Dopamine agonists

Can increase the amount of dopamine in the brain. 

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Antiseizure medicines

Can prevent seizures. 

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Supplements that are useful include: 

Vitamin B6

This is a “helper” molecule for many enzymes. Vitamin B6 can help the AADC enzyme work better. 

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Can help with sleep. 

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Other forms of support include: 

Feeding support

Many children with this disorder will need a tube placed for feeding. 

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Developmental therapies

These may involve: 

  • Speech therapy 
  • Physical therapy 
  • Occupational therapy 
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Psychosocial support for families

This might involve a social worker or psychotherapist. 

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Individualized education plan

This is a program set up with schools. It works to ensure that every child get the best education possible for them. 


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Most children with this disorder present with severe symptoms. As a result, many do not live through childhood. A small number of children have milder forms of the disease. They may reach adulthood. Usually, after infancy, signs and symptoms do not worsen with time.  




AADC Family Network 
The ALADD Foundation, Inc. (now known as AADC Family Network) was established in 1998 and was the first foundation for AADC (Aromatic L Amino Acid Decarboxylase Deficiency). The foundation was established for the charitable and educational purposes of providing research, medical assistance, support, and awareness, and to participate in all services and activities designed to carry out and find a cure for AADC. You will find resources for physicians, helpful instructional care videos, and more to help you answer the question of “what now” on the website. Families can register with the foundation and apply for funding. AADC Family Network hosts a private Facebook group for families and caregivers. 

Childhood Stroke 1


PTC Pinpoint Neurotransmitter Disorders Program

For children with symptoms of neurotransmitter disorders, such as AADC deficiency, PTC Therapeutics and Invitae are offering no-cost genetic testing, post-test genetic counseling, and family screening through the PTC Pinpoint Neurotransmitter Disorders Program.

One of the most common symptoms of AADC deficiency is involuntary eye movements called oculogyric crisis (see video here). These are moments when a child’s eyes suddenly roll upward or to the side involuntarily.

Talk to your doctor about testing with PTC Pinpoint if your child is experiencing symptoms of AADC deficiency. Also, check out this video to learn more about the Patient Engagement Team at PTC Therapeutics.

Child Neurology Foundation (CNF) solicits resources from the community to be included on this webpage through an application process. CNF reserves the right to remove entities at any time if information is deemed inappropriate or inconsistent with the mission, vision, and values of CNF. 

Research for Aromatic L-Amino Acid Decarboxylase Deficiency (AADC) are clinical trials that are recruiting or will be recruiting. Updates are made daily, so you are encouraged to check back frequently. is a database of privately and publicly funded clinical studies conducted around the world. This is a resource provided by the U.S. National Library of Medicine (NLM), which is an institute within the National Institutes of Health (NIH). Listing a study does not mean it has been evaluated by the U.S. Federal Government. Please read the NLM disclaimer for details.  

Before participating in a study, you are encouraged to talk to your health care provider and learn about the risks and potential benefits. 

Additional clinical trial information for AADC can be found here:

The information in the CNF Child Neurology Disorder Directory is not intended to provide diagnosis, treatment, or medical advice and should not be considered a substitute for advice from a healthcare professional. Content provided is for informational purposes only.  CNF is not responsible for actions taken based on the information included on this webpage. Please consult with a physician or other healthcare professional regarding any medical or health related diagnosis or treatment options. 


Himmelreich N, Montioli R, Bertoldi M, et al. Aromatic amino acid decarboxylase deficiency: Molecular and metabolic basis and therapeutic outlook. Molecular Genetics and Metabolism. 2019; 127(1):12-22.  

Hyland K and Reott M. Prevalence of aromatic L-amino acid decarboxylase deficiency in at-risk populations. Pediatric Neurology. 2020; 106:38-42.  

Wassenberg T, Molero-Luis M, Jeltsch K, et al. Consensus guideline for the diagnosis and treatment of aromatic L-amino acid decarboxylase (AADC) deficiency. Orphanet J Rare Dis. 2017;12:12.  

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