Screening and diagnosis of β-ureidopropionase deficiency by gas chromatographic/mass spectrometric analysis of urine

✍ Scribed by Morimasa Ohse; Masafumi Matsuo; Akihito Ishida; Tomiko Kuhara

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 157 KB
• Volume: 37
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.354

✦ Synopsis

Abstract

Dihydropyrimidine dehydrogenase (DHPDase), dihydropyrimidinase (DHPase) and β‐ureidopropionase (βUPase) are the enzymes that catalyze the first, second, and third steps of the degradation of pyrimidines, respectively. β‐Ureidopropionate (βUP) and β‐ureidoisobutyrate (βUIB) are increased in the urine of patients with βUPase deficiency. The original case in which βUPase deficiency was discovered by NMR spectroscopy was an 11‐month‐old patient who presented with hypotonia and dystonic movement. We detected a second but asymptomatic case during a pilot study of neonatal screening with filter‐paper urine, urease pretreatment and gas chromatography/mass spectrometry (GC/MS). The urease pretreatment of urine without fractionation resulted in a high recovery of these polar ureide compounds and allowed the highly sensitive GC/MS detection and diagnosis of βUPase deficiency. βUP and βUIB were identified using GC/MS techniques. In the urine of the neonate with βUPase deficiency, βUP and βUIB were persistently increased. Thymine, 5,6‐dihydrothymine and 5,6‐dihydrouracil were increased only moderately but significantly. It is known that thymine and uracil increase markedly in DHPDase deficiency, and 5,6‐dihydrothymine and 5,6‐dihydrouracil increase in DHPase deficiency. Therefore, βUPase deficiency can be differentially diagnosed from the first and second enzyme deficiencies. Application of this specific and sensitive diagnostic procedure will lead to an understanding of the clinical heterogeneity of βUPase deficiency. Furthermore, the identification of patients with defects in pyrimidine metabolism will enable doctors to avoid cancer chemotherapy with pyrimidine analogues such as 5‐fluorouracil, which could be dangerous for these patients. Copyright © 2002 John Wiley & Sons, Ltd.