Aromatic L-amino acid decarboxylase deficiency (NORD)

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Aromatic L-amino acid decarboxylase deficiency (NORD)

Information for patients and families

The National Organization for Rare Disorders (NORD)

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Aromatic L-amino acid decarboxylase deficiency (NORD)

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Aromatic L-Amino Acid Decarboxylase deficiency, or simply AADC deficiency, is a very rare disease in which there’s a decreased activity of an enzyme called aromatic l-amino acid decarboxylase, or AADC for short.

The disease affects babies, which most often seem healthy at birth, but then start developing signs and symptoms during the first months of life.

The severity of the disease can vary between individuals.

AADC deficiency mainly causes movement disorders.

One of the most frequent symptoms is hypotonia of the trunk, which means these individuals have very little muscle tone, making them floppy.

Another frequent symptom is oculogyric crises, which is the abnormal rotation of the eyeballs with elevation of the gaze, as well as uncontrolled movements of the head and neck, agitation, and irritability.

Oculogyric crises can last for hours, and typically occur every 2 to 5 days.

Other less frequent movement disorders include decreased movement called hypokinesia, increased muscle tone of the limbs or hypertonia, and involuntary movements like tremors, twisting movements called dystonia, writhing movements or athetosis, dance-like movements of hands and feet called chorea.

AADC deficiency can also affect the autonomic nervous system, which is the part of the nervous system that controls our internal organs.

Symptoms can include excessive salivation and sweating, droopy eyelids called ptosis, nasal congestion, unstable body temperature, low blood pressure, and low blood sugar or hypoglycemia.

In addition, AADC deficiency can cause gastrointestinal symptoms like reflux, diarrhea, or constipation.

Other less frequent symptoms include seizures, decreased or increased sleep, and decreased or increased reflexes.

Finally, children affected with AADC deficiency often have learning disabilities, developmental delay, and fail to reach milestones like talking or walking.


Aromatic L-amino acid decarboxylase deficiency (AADC) is an autosomal recessive disorder caused by mutations in the Dopa Decarboxylase (DDC) gene. AADC is an enzyme involved in the synthesis of dopamine and serotonin, which are important neurotransmitters responsible for the communication among neurons. This condition is characterized by impaired cognitive development, decreased muscle tone, failure to thrive, abnormal eye movements, and a wide range of other neurologic symptoms.


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