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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

Perform2
  • CSF neurotransmitter metabolite panel
  • Plasma enzyme activity assay
Interpret2
  • 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
Decreased
AADC
enzyme activity
CSF
High levels of
3-OMD
L-dopa
5-HTP
Low levels of
5-HIAA
HVA
MHPG
Normal pterins
Genetic testing
Variants
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.