Title: Screening and diagnosis of tetrahydrobiopterin responsive phenylalanine hydroxylase deficiency with tetrahydrobiopterin loading test
Abstract: Objective Tetrahydrobiopterin (BH 4) responsive phenylalanine hydroxylase (PAH) deficiency is one of the forms of phenylketonuria (PKU). The aim of this study was to screen and diagnose BH 4 responsive PAH deficiency, to further understand its clinical characteristics, and to provide evidence for applying BH 4 drug therapy. Methods BH 4 20 mg/kg loading test was performed in 73 patients with hyperphenylalaninemia (HPA) (47 males and 26 females), the mean age was 1.93 months. Combined phenylalanine(100 mg/kg) and BH 4 loading test was performed if patients had a basic blood phenylalanine concentration less than 600 μmol/L. The urine pterin profile analysis and the dihydropteridine reductase (DHPR) activity in dry blood filter spot were analyzed simultaneously. The patients with BH 4 responsive PAH deficiency were treated with BH 4 tablets (10-20 mg/kg·d) under normal diet for 6 to 7 days. Their blood phenylalanine concentration was checked. Results (1)The characteristic curve of phenylalanine level was observed in 73 patients after BH 4 loading test. Twenty-two patients were diagnosed as classic phenylketonuria (PKU), 39 were moderate PKU and 12 were BH 4 deficiency. (2)Twenty-two (56.4%) of 39 moderate PKU patients were found to be responsive to BH 4 and the blood phenylalanine was decreased by at least 30%. (3) Six patients with BH 4 responsive PAH deficiency were treated with BH 4 for 6 to 7 days, 4 patients had a normal phenylalanine concentration after 10 mg/kg BH 4 supplement, while other 2 patients needed a treatment of BH 4 at 20 mg/kg. Conclusion Some patients with moderate PKU caused by phenylalanine hydroxylase deficiency were responsive to BH 4. Their blood phenylalanine significantly decreased after oral BH 4 loading. The BH 4 loading test is an effective diagnostic method to detect BH 4 sensitivity in PKU patients. BH 4 responsive PAH deficiency patient could be treated with BH 4 to replace low-phenylalanine diet treatment totally or partially, which may provide an optional treatment for the disease and improve the quality of life of the patients.
Publication Year: 2005
Publication Date: 2005-01-01
Language: en
Type: article
Access and Citation
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot