Aromatic L-amino acid decarboxylase deficiency diagnosed by clinical metabolomic profiling of plasma

Mol Genet Metab. Jun-Jul 2015;115(2-3):91-4. doi: 10.1016/j.ymgme.2015.04.008. Epub 2015 May 2.

Abstract

Aromatic L-amino acid decarboxylase (AADC) deficiency is an inborn error of metabolism affecting the biosynthesis of serotonin, dopamine, and catecholamines. We report a case of AADC deficiency that was detected using the Global MAPS platform. This is a novel platform that allows for parallel clinical testing of hundreds of metabolites in a single plasma specimen. It uses a state-of-the-art mass spectrometry platform, and the resulting spectra are compared against a library of ~2500 metabolites. Our patient is now a 4 year old boy initially seen at 11 months of age for developmental delay and hypotonia. Multiple tests had not yielded a diagnosis until exome sequencing revealed compound heterozygous variants of uncertain significance (VUS), c.286G>A (p.G96R) and c.260C>T (p.P87L) in the DDC gene, causal for AADC deficiency. CSF neurotransmitter analysis confirmed the diagnosis with elevated 3-methoxytyrosine (3-O-methyldopa). Metabolomic profiling was performed on plasma and revealed marked elevation in 3-methoxytyrosine (Z-score +6.1) consistent with the diagnosis of AADC deficiency. These results demonstrate that the Global MAPS platform is able to diagnose AADC deficiency from plasma. In summary, we report a novel and less invasive approach to diagnose AADC deficiency using plasma metabolomic profiling.

Keywords: 3-O-methyldopa; 3-methoxytyrosine; Aromatic l-amino acid decarboxylase deficiency; Metabolomic profiling; Oculogyric crisis.

Publication types

  • Case Reports

MeSH terms

  • Amino Acid Metabolism, Inborn Errors / blood*
  • Aromatic-L-Amino-Acid Decarboxylases / blood
  • Aromatic-L-Amino-Acid Decarboxylases / deficiency*
  • Dihydroxyphenylalanine / analogs & derivatives
  • Dihydroxyphenylalanine / blood
  • Dopa Decarboxylase / genetics*
  • Humans
  • Infant
  • Male
  • Metabolomics / methods*
  • Polymorphism, Single Nucleotide*
  • Tyrosine / analogs & derivatives
  • Tyrosine / blood

Substances

  • Tyrosine
  • Dihydroxyphenylalanine
  • Dopa Decarboxylase
  • Aromatic-L-Amino-Acid Decarboxylases
  • 3-methoxytyrosine

Supplementary concepts

  • Aromatic amino acid decarboxylase deficiency