Clinical Guidance

The aromatic L-amino acid decarboxylase (AADC) enzyme catalyzes the last step in the biosynthesis of the monoamine neurotransmitters dopamine and serotonin. Dopamine itself is a precursor for the synthesis of epinephrine and norepinephrine. Therefore, the clinical features of AADC deficiency are caused by a severe combined deficiency of dopamine, serotonin, epinephrine, and norepinephrine. Individuals with AADC deficiency typically have complex symptoms, including motor, behavioral, cognitive, and autonomic findings. Symptom onset is in early infancy, typically within the first six months of life . The most common initial symptoms are often nonspecific, and include feeding difficulties, hypotonia, and developmental delay. The key to clinical diagnosis lies in the subsequent recognition of a constellation of symptoms that suggest a monoamine neurotransmitter disorder: oculogyric crises (which occur in the vast majority of affected individuals, typically starting in infancy), movement disorders (especially dystonia), and autonomic dysfunction (excessive sweating, temperature instability, ptosis, nasal congestion, hypoglycemic episodes) . To date, about 350 individuals have been reported with AADC deficiency . The following description of the phenotypic features associated with this condition is based on these reports. Table 2. Select Features of Aromatic L-Amino Acid Decarboxylase Deficiency

Diagnostic Criteria

Consensus clinical diagnostic criteria for aromatic L-amino acid decarboxylase (AADC) deficiency have been published .

Suggestive Findings

AADC deficiency should be considered in individuals with the following clinical and supportive laboratory findings and family history.

Clinical findings

Source: GeneReviews — "Aromatic L-Amino Acid Decarboxylase Deficiency"

Management Guidelines

Consensus clinical practice guidelines for aromatic L-amino acid decarboxylase (AADC) deficiency have been published .

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with AADC deficiency, the evaluations summarized (if not performed as part of the evaluation that led to diagnosis) are recommended.

Surveillance Guidelines

To monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations, the evaluations summarized in are recommended. Table 7. Aromatic L-Amino Acid Decarboxylase Deficiency: Recommended Surveillance