DESCRIPTION
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.
CAUSES
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.
OUTLOOK
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.
Resources
ORGANIZATIONS/GROUPS
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.
ADDITIONAL RESOURCES
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.
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