Application of isoxanthopterin as a new pterin marker in the differential diagnosis of hyperphenylalaninemia.

Background: This study aimed to explore the value of applying a new pterin marker (isoxanthopterin) to the traditional urine pterin analysis to reduce the rate of mis-diagnosis of 6-pyruvoyltetrahydropterin synthase deficiency (PTPSD) and improve the accuracy of diagnosis.

Methods: We compared the urine neopterin (N), biopterin (B), isoxanthopterin (Iso), B% and Iso% levels between patients with phenylalanine hydroxylase deficiency and those with PTPSD, and found the most specific pterin biomarkers by ROC analysis. A positive cut-off value of urine pterins was determined.

QDPR gene mutation and clinical follow-up in Chinese patients with dihydropteridine reductase deficiency.

Background: This study aimed to investigate the mutation spectrum of the QDPR gene, to determine the effect of mutations on dihydropteridine reductase (DHPR) structure/function, to discuss the potential genotypephenotype correlation, and to evaluate the clinical outcome of Chinese patients after treatment.

Methods: Nine DHPR-deficient patients were enrolled in this study and seven of them underwent neonatal screening. QDPR gene mutations were analyzed and confirmed by routine methods.