Fast Five Quiz: Aromatic L-amino Acid Decarboxylase Deficiency (AADCD) Clinical Characteristics

Stephen L. Nelson, Jr, MD, PhD


August 13, 2021

Figure 1. DNA mutation, conceptual image.

Normal CSF pterins are critical to diagnosis as they clearly differentiate AADCD from the tetrahydrobiopterin disorders.

Although regression of language skills has been described, a deteriorating clinical course is not characteristic of AADCD and should prompt suspicion for other diseases and a thorough diagnostic workup.

The CSF profile of AADCD may be similar to that of pyridox(am)ine 5-phosphate (PNPO) deficiency. But additional findings of PNPO deficiency differentiate the two conditions during workup — namely, a severe neonatal epileptic encephalopathy, as well as increased glycine and threonine in CSF and a very low level of proteolipid protein.

Increased urinary vanillactic acid should prompt suspicion for AADCD, but normal levels do not exclude the diagnosis. Dopamine, homovanillic acid (HVA), and vanillylmandelic acid in urine are also unreliable biomarkers.

Learn more about AADCD diagnosis.


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