The Paradox of Hyperdopaminuria in Aromatic l-Amino Acid Deficiency Explained

Aromatic l-amino acid decarboxylase (AADC) decarboxylates 3,4-l-dihydroxylphenylalanine (l-dopa) to dopamine, and 5-hydroxytryptophan to serotonin. In AADC deficiency, dopamine and serotonin deficiency leads to a severe clinical picture with mental retardation, oculogyric crises, hypotonia, dystonia, and autonomic dysregulation. However, despite dopamine deficiency in the central nervous system, urinary dopamine excretion in AADC-deficient patients is normal to high.