Fast Five Quiz: Aromatic L-Amino Acid Decarboxylase Deficiency Diagnosis and Management

Stephen L. Nelson, Jr, MD, PhD; Germaine L. Defendi, MD, MS, FAAP


February 07, 2022

Figure 1. Genetic mutation, conceptual image.

At least two of the following three core diagnostic test results should be positive to confirm a diagnosis of AADC deficiency:

  • Decreased plasma AADC enzyme activity

  • Low CSF levels of 5-HIAA, HVA, and MHPG; increased CSF levels of 3-OMD, L-dopa, and 5-HTP; and normal levels of CSF pterins

  • Compound heterozygous or homozygous pathogenic variants in the DDC gene

If the first step performed is genetic testing, functional confirmation should be completed by measuring plasma AADC enzyme activity and/or the neurotransmitter metabolites in CSF. If plasma and CSF studies are positive, therapy should be started immediately and not delayed pending results of molecular genetic testing. Of note, all three of these key diagnostic tests are recommended.

Learn more about the diagnosis of AADC deficiency.


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