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Aromatic l-amino acid decarboxylase deficiency
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Reviewed May 2008
What is aromatic l-amino acid decarboxylase deficiency?
Aromatic l-amino acid decarboxylase (AADC) deficiency is an inherited disorder that affects the way signals are passed between certain cells in the nervous system.
Signs and symptoms of AADC deficiency generally appear in the first year of life. Affected infants may have severe developmental delay, weak muscle tone (hypotonia), muscle stiffness, difficulty moving, and involuntary writhing movements of the limbs (athetosis). They may be lacking in energy (lethargic), feed poorly, startle easily, and have sleep disturbances. People with AADC deficiency may also experience episodes called oculogyric crises that involve abnormal rotation of the eyeballs; extreme irritability and agitation; and pain, muscle spasms, and uncontrolled movements, especially of the head and neck.
AADC deficiency may affect the autonomic nervous system, which controls involuntary body processes such as the regulation of blood pressure and body temperature. Resulting signs and symptoms can include droopy eyelids (ptosis), constriction of the pupils of the eyes (miosis), inappropriate or impaired sweating, nasal congestion, drooling, reduced ability to control body temperature, low blood pressure (hypotension), backflow of acidic stomach contents into the esophagus (gastroesophageal reflux), low blood sugar (hypoglycemia), fainting (syncope), and cardiac arrest.
Signs and symptoms of AADC deficiency tend to worsen late in the day or when the individual is tired, and improve after sleep.
How common is aromatic l-amino acid decarboxylase deficiency?
AADC deficiency is a very rare disorder. Only about 30 people with this condition have been identified worldwide.
What genes are related to aromatic l-amino acid decarboxylase deficiency?
Mutations in the DDC gene cause AADC deficiency. The DDC gene provides instructions for making the AADC enzyme, which is important in the nervous system. This enzyme helps produce dopamine and serotonin from other molecules. Dopamine and serotonin are neurotransmitters, which are chemical messengers that transmit signals between nerve cells, both in the brain and spinal cord (central nervous system) and in other parts of the body (peripheral nervous system).
Mutations in the DDC gene result in reduced activity of the AADC enzyme. Without enough of this enzyme, nerve cells produce less dopamine and serotonin. Dopamine and serotonin are necessary for normal nervous system function, and changes in the levels of these neurotransmitters contribute to the developmental delay, intellectual disability, abnormal movements, and autonomic dysfunction seen in people with AADC deficiency.
Read more about the DDC gene.
How do people inherit aromatic l-amino acid decarboxylase deficiency?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of aromatic l-amino acid decarboxylase deficiency?
These resources address the diagnosis or management of aromatic l-amino acid decarboxylase deficiency and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about aromatic l-amino acid decarboxylase deficiency?
You may find the following resources about aromatic l-amino acid decarboxylase deficiency helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for aromatic l-amino acid decarboxylase deficiency?
What if I still have specific questions about aromatic l-amino acid decarboxylase deficiency?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding aromatic l-amino acid decarboxylase deficiency?
amino acid ; autonomic nervous system ; autosomal ; autosomal recessive ; cardiac ; cardiac arrest ; cell ; central nervous system ; deficiency ; developmental delay ; dopamine ; enzyme ; esophagus ; fainting ; gastroesophageal reflux ; gene ; hypoglycemia ; hypotension ; hypotonia ; involuntary ; lacking in energy ; lethargic ; muscle tone ; nervous system ; neurotransmitters ; peripheral ; peripheral nervous system ; ptosis ; recessive ; stomach ; syncope
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (7 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.