Abnormal glucose metabolism in aromatic l-amino acid decarboxylase deficiency

We report sibling cases of aromatic l-amino acid decarboxylase (AADC) deficiency, which is a very rare congenital metabolic disorder. These patients were born to healthy and non-consanguineous parents, and presented oculogyric crises, paroxysmal dystonic attacks, and severe psychomotor retardation since early infancy. In cerebrospinal fluid the levels of homovanilic acid and 5-hydroxyindoleacetic acid were very low and the level of l-dopa was very high. The diagnosis was confirmed by the lack of AADC activity in plasma, and a point mutation in the AADC gene. MRI revealed a slightly small volume of the prefrontal areas and normal myelination in both patients. Positron emission tomography using 2-deoxy-2[18F] fluoro-d-glucose was performed in one patient, which revealed hypometabolism in the prefrontal cortex and bilateral basal ganglia with a little laterality. These findings suggested that the severe dystonic features were caused by abnormal function of bilateral basal ganglia and severe psychomotor retardation could be due to abnormalities in prefrontal cortical activity.