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The diagnostic approach to AADC Deficiency

Earlier identification can help improve the care and management of patients with AADC Deficiency1-3

The diagnostic pathway for suspected AADC Deficiency2,4

How AADC Deficiency is diagnosed

Diagnostic tests that identify AADC Deficiency2

Currently, these core tests can help diagnose AADC Deficiency2

  • CSF neurotransmitter metabolite panel
  • Plasma enzyme activity assay
  • Reduced HVA, 5-HIAA, and MHPG; elevated 3-OMD, L-dopa, and 5-HTP, and normal pterins in CSF
  • AND/OR
  • Low plasma AADC enzyme activity
  • Increased urinary VLA
Confirm with genetic testing2
  • Mutation(s) in the DDC gene

3-OMD=3-O-methyldopa; 5-HIAA=5-hydroxyindoleacetic acid; 5-HTP=5-hydroxytryptophan; CSF=cerebrospinal fluid; HVA=homovanillic acid; L-dopa=L-3,4-dihydroxyphenylalanine; MHPG=3-methoxy-4-hydroxyphenylglycol; VLA=vanillactic acid.

Other diagnostic tests that may be helpful2

  • Blood level measurement of 3-OMD
  • Urinary organic acid analysis

AADC Deficiency diagnostic workup

Blood plasma
enzyme activity
High levels of
Low levels of
Normal pterins
Genetic testing
in DDC gene

Consensus guidelines recommend confirming an AADC Deficiency diagnosis with a genetic test2 

Additional considerations when suspecting AADC Deficiency:

  • Other specialties may be able to assist in diagnosis, such as a movement disorder specialist or clinical geneticist
  • Consider consulting with specialists located within academic centers that have experience with rare disease diagnosis and management

Useful resources 

Visit the Resources page for a list of helpful links and downloadable information.

AADC Deficiency Resources

References: 1. Manegold C, Hoffmann GF, Degen I, et al. Aromatic L-amino acid decarboxylase deficiency: clinical features, drug therapy and follow-up. J Inherit Metab Dis. 2009;32(3):371-380. 2. Wassenberg T, Molero-Luis M, Jeltsch K, et al. Consensus guideline for the diagnosis and treatment of aromatic l-amino acid decarboxylase (AADC) deficiency. Orphanet J Rare Dis. 2017;12(1):12. doi: 10.1186/s13023-016-0522-z. 3. Brun L, Ngu LH, Keng WT, et al. Clinical and biochemical features of aromatic L-amino acid decarboxylase deficiency. Neurology. 2010;75(1):64-71. 4. Garcia-Cazorla A, Duarte S, Serrano M, et al. Mitochondrial diseases mimicking neurotransmitter defects. Mitochondrion. 2008;8(3):273-278.