1. The Facts

    The Facts

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  2. Neurotransmitters

    Neurotransmitters

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  3. Symptoms


    Symptoms

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  4. Diagnosing


    Diagnosing

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  5. Treating


    Treating

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  6. A Family Affected


    A Family Affected

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How is AADC Deficiency diagnosed?


The clinical picture in AADC is similar to that of tyrosine hydroxylase deficiency (TH), guanosine triphosphate cyclohydrolase (GTPCH) deficiency, sepiapterin reductase (SR) deficiency as well as other dopamine related diseases. CSF analysis of certain neurotransmitter metabolites can help distinguish between all of these conditions and each of these conditions requires separate therapies. This is why it is best to have the lumbar puncture.

1)Cerebrospinal Fluid/CSF (lumbar Puncture)

A sample of cerebrospinal fluid (CSF) is taken from a child suspected of having AADC deficiency (or other similar dopamine related disease). The CSF can provide an almost conclusive positive result for AADC deficiency as well as eliminating other dopamine related diseases. There are just a few laboratories in the world able to confirm AADC deficiency by measuring HVA, 5-HIAA, 3-O-methylDOPA,L-DOPA, 5-hydroxytryptophan (5-HTP)and vanillyllactic acid in a CSF sample.

An example of a positive AADC result from CSF:

HPLC Diagnosis of AADC Deficiency

High Performance Liquid Chromatography with Electrochemical Detection

High Performance Liquid Chromatography with Electrochemical Detection

5-HIAA = 5-hydroxyindoleacetic acid - a serotonin metabolite
HVA = homovanillic acid = a dopamine metabolite
5HTP = 5-hydroxytryptophan - a serotonin precursor that accumulates in AADC deficeincy
3-OMD = 3-O-methyldopa a methylated derivative of levodopa that accumulates in AADC deficiency.

2) Blood Test (plasma enzyme assay)

Although a lumbar puncture is preferred (because it can distinguish between several diseases that present with similar symptoms) a blood test to determine enzyme activity can also be used to give a diagnosis of AADC deficiency.

This procedure can be used to confirm the findings of an already performed lumbar puncture or confirm a diagnosis of AADC deficiency if a parent of a child suspected to have this condition refusesto allow a lumbar to be performed.

This test will determine how active AADC function is and a diagnosis of AADC will be confirmed if the activity of AADC function is almost undetectable.

The parents of an affected AADC child can have the same test to conclusively confirm their child's diagnosis and confirm that they are carriers of a mutated gene allele for AADC deficiency. See ‘Is AADC Deficiency an inherited disease’.

The same test is also available to other family members (including the siblings of an AADC affected child) to determine if they are carriers of the same mutated gene allele for AADC deficiency.

This test requires strict collection procedures. Blood should be drawn according to the specific procedure policies provided by each of the laboratories in the section ‘where does my child’s sample go to confirm diagnosis’.

3) Blood Test (DNA Analysis)

The gene for AADC deficiency maps to chromosome 7p12.1-p12.3. Blood can be collected and DNA extracted which can allow sequencing of the whole of the coding region for the AADC gene (exon/exon-intron boundary sequencing). This means that if a mutation(s) is/are found an absolutely diagnosis is made. Detection of mutations in an affected child also means that prenatal diagnosis should be available for subsequent pregnancies.

This test requires strict collection procedures. Blood should be drawn according to the specific procedure policies provided by each of the laboratories in the section ‘where does my child’s sample go to confirm diagnosis’.

4) Urine collection (to measure neurotransmitter activity)

Although a urine sample is not the usual or widely used method to confirm (or make the initial diagnosis) of AADC deficiency (descriptions 1, 2 and 3 are the preferred) there is some evidence that this may be possible. A diagnosis of AADC Deficiency has been confirmed using a urine sample alone measuring HVA, 5-HIAA, pteridines, L-DOPA, 5-HTP, vanilyllactic acid and 3-0-methylDOPA. Further studies are necessary to measure how accurate this method is. Urine measurement of vanillactic acid can also detect AADC deficiency but elevations of vanillactic acid are small and it requires laboratories to specifically look for this chemical.


Contact Information

  • E-mail: enquiries@aadcresearchtrust.org
  • Telephone: +44 (0) 208 651 6450
  • Address: The AADC Research Trust, t/as eBear's Attic Tea Room & Charity Boutique, 320 Limpsfield Road, Warlingham, Surrey CR2 9BX