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The clinical presentation of inborn errors of pyrimidine degradation varies considerably from asymptomatic to severe neurological illness. We have reported a method to screen for and make a chemical diagnosis of beta-ureidopropionase deficiency, leading to the discovery of the first asymptomatic case of this disease. In this method, the recovery of beta-ureidopropionate and beta-ureidoisobutyrate, the key biomarkers, was very high,and the adoption of GC/MS and targeted analysis enabled us to simultaneously obtain information related and unrelated to pyrimidine metabolism. The present study reports the results of a large-scale screening of 24,000 newborns using dried urine on filter paper. Identification of a total of four asymptomatic patients among newborns suggests the high incidence (1/6000) of this disease in Japan. While these newborns were asymptomatic, two additional cases detected at the age of 5 years as well as 3 months with this method for high-risk screening had autism and West syndrome, respectively.The key biomarkers and alpha-ureidobutyrate used as an internal standard were found to give not only their di-trimethylsilyl derivatives but also tri-trimethylsilyl derivatives, upon derivatization. The mass spectra and retention times of their tri-trimethylsilyl derivatives and data handling for quantification of the markers are presented.Identification of individuals with defects in pyrimidine metabolism would realize personalized medication in cancer chemotherapy with pyrimidine analogs such as 5-fluorouracil., (Copyright (c) 2008 John Wiley & Sons, Ltd.)

Propionic acidaemia (McKusick 23200) is caused by reduced activity of propionyl-CoA carboxylase (EC 6.4.1.3). A number of metabolites characteristic of this disease are excreted in patients' urine. We have developed a method of chemical diagnosis using gas chromatography-mass spectrometry (GC-MS). Since our first chemical diagnosis (Matsumoto et al., 1978), we have diagnosed seven patients. Profiles of urinary acids, however, varied from patient to patient. Factors affecting these profiles may be genetic make-up, age, or the patient's clinical and nutritional conditions. We have compared two metabolic profiles of a girl under different clinical conditions and found increased excretion of acetyl-CoA precursors during clinical episodes.