title: Comprehensive analysis of pyrimidine metabolism in 450 children with unspecific neurological symptoms using high-pressure liquid chromatography-electrospray ionization tandem mass spectrometry.
abstract: To evaluate the significance of inborn metabolic disorders of the pyrimidine degradation pathway, 450 children with unspecific neurological symptoms were comprehensively studied; 200 healthy children were recruited as controls. Uracil and thymine as well as their degradation products in urine were determined with an improved method based on reversed-phase HPLC coupled with electrospray ionization tandem mass spectrometry and detection by multiple-reaction monitoring using stable-isotope-labelled reference compounds as internal standards. From the results of the control group we established age-related reference ranges of all pyrimidine degradation products. In the patient group, two children with dihydropyrimidine dehydrogenase (DPYD) deficiency were identified; one of these was homozygous for the exon 14-skipping mutation of the DPYD gene. In addition, two patients with high uracil, dihydrouracil and beta-ureidopropionate were found to have ornithine transcarbamylase deficiency. In the urine of 9 patients, beta-alanine was markedly elevated owing to treatment with vigabatrin, an irreversible inhibitor of GABA transaminase, which interferes with beta-alanine breakdown. Four patients had exclusively high levels of beta-aminoisobutyrate (beta-AIB) due to a low activity of the D-beta-AIB-pyruvate aminotransferase, probably without clinical significance. In conclusion, quantitative investigation of pyrimidine metabolites in children with unexplained neurological symptoms, particularly epileptic seizures with or without psychomotor retardation, can be recommended as a helpful tool for diagnosis in clinical practice. Sensitive methods and age-related reference ranges enable the detection of partial enzyme deficiencies.
authors.affiliation: Division of Metabolic and Endocrine Diseases, University Children's Hospital, Heidelberg, Germany. christiane_schmidt@med.uni-heidelberg.de
authors.forename: C
authors.initials: C
authors.lastname: Schmidt
authors.forename: U
authors.initials: U
authors.lastname: Hofmann
authors.forename: D
authors.initials: D
authors.lastname: Kohlmüller
authors.forename: T
authors.initials: T
authors.lastname: Mürdter
authors.forename: U M
authors.initials: UM
authors.lastname: Zanger
authors.forename: M
authors.initials: M
authors.lastname: Schwab
authors.forename: G F
authors.initials: GF
authors.lastname: Hoffmann
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D054067:Dihydropyrimidine Dehydrogenase Deficiency; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000235:genetics; D004827:Epilepsy / Q000175:diagnosis; D005091:Exons; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007477:Ions; D008297:Male; D013058:Mass Spectrometry; D015233:Models, Statistical; D009154:Mutation; D016011:Normal Distribution; D020163:Ornithine Carbamoyltransferase Deficiency Disease; D011743:Pyrimidines / Q000378:metabolism*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013941:Thymine / Q000737:chemistry; D014498:Uracil / Q000737:chemistry; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D007477:Ions; D011743:Pyrimidines; D015091:beta-Alanine; C035122:N-carbamoyl-beta-alanine; D014498:Uracil; D042943:Dihydrouracil Dehydrogenase (NADP); C030986:pyrimidine; D013941:Thymine