A Case of Dihydropteridine Reductase Deficiency

Abstract

Tetrahydrobiopterin (BH4) is the essential cofacter of phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp) hydroxylases . BH4 deficiency, a rare but severe type of hyperphenylalaninemia, is characterized by progressive neurologic symptoms despite early detection and treatment with a Phe-restricted formula. An expensive dose of BH4 is needed to keep with the Phe, Tyr and Trp hydroxylation reaction. Severe BH4 deficiency is a naturally occurring model of cerebral catecholamine and serotonin shortage. Here we present a patient in which the hyperpheny lalaninelTIia could be reversed with BH4 therapy, but the concentrations of homo vanillic acid (HVA ) and 5- hydroxy indole acetic acid (5HIAA) in cerebrospinal fluid (CSF) remained low. Administration of the neurotransmitter precursors iL-DOPA/carbidopa and 5-hydroxytryptophan jappeared to be the most effective treatment and may prevent neurological damage if started early in life

Keywords

• tetrahydrobiopterin(bh4) loading test
• dihydropteridine reductase (dhpr)
• hyperprolactinemia
• neurotransmitter precursor
• homovanillic acid (hva)
• 5-hydroxyindole acetic acid (5hiaa)
• 5- hydroxy tryptophan (5-htp)
• quinonoid dihydrobiopterin (qbh2)' phenylketonuria (pku)