Kelly Heger, Founder of the AADC Family Network, provides an overview of aromatic L-amino acid decarboxylase (AADC) deficiency and her family’s diagnostic journey with the disorder. Kelly is the mother and caregiver of Jillian Heger, who lives with AADC deficiency. You can see a short video of Kelly and her family here.
Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare genetic disorder that affects the nervous and musculoskeletal systems of young patients. It is caused by defect in the dopa decarboxylase (DDC) gene, which leads to a reduction in the critical neurotransmitters dopamine, norepinephrine, epinephrine, and melatonin in the brain.
The first sign of the disease is generally hypotonia (e.g., the neck muscles are too weak to hold the baby’s head up). Other neurological problems, including developmental delay (e.g., walking and talking), movement disorders (e.g., involuntary movements), and autonomic issues (e.g., excessive sweating, chronic nasal congestion, hypotension, uncontrolled heart rate, and ptosis), are common; patients may have one or more of these signs.
One movement disturbance that can be extremely concerning to caregivers of patients with AADC deficiency is a syndrome called oculogyric crisis, which is typified by a patient’s abnormal rotation of the eyeballs, muscle spasms, and uncontrolled head and neck muscle action. Symptoms tend to worsen with fatigue and improve after the patient sleeps.
Once suspected, a diagnosis is challenging: analysis of metabolites in cerebrospinal fluid, assessment of plasma AADC activity, and/or DNA sequence analysis is required. Blood testing and cerebrospinal fluid analysis will show very low levels of specific chemicals (e.g., 5-hydroxyindoleacetic acid) related to the production of the neurotransmitters dopamine and serotonin. Blood tests can measure the activity of the enzyme that is encoded by the DDC gene. Genetic testing for DDC mutations will confirm the diagnosis. Brain imaging and electroencephalographic monitoring findings in patients with AADC are typically normal.
To learn more about this rare genetic disorder, visit our AADC Deficiency Learning Page.
