Biogenic amine synthesis defect in dihydropteridine reductase deficiency.

In the enzymatic hydroxylation of aromatic amino acids, tetrahydrobiopterin is the essential cofactor. Regeneration of tetrahydrobiopterin requires dihydropteridine reductase, without which there should be a deficiency of hydroxylated amino acids and their products, biogenic amines. Assay of biopsied brain cortex of a patient with a deficiency of dihydropteridine reductases showed low concentrations of serotonin and dopamine, and this was reflected in the concentrations of their major metabolites measured in cerebrospinal fluid from lumbar, ventricular, and subarachnoid spaces. The metabolite concentrations were restored to normal, or above normal, by treatment with specific amino acids which bypass the metabolic block at the hydroxylation step. It is postulated that the seizures and neurological deterioration of the patient were related to a deficiency in the synthesis of biogenic amine neurotransmitters.