Urinary pterins in atypical phenyl-ketonuria: 60

Abstract

Three further patients with atypical PKU caused by tetrahydrobiopterin deficiency were investigated: D.K. (B. Blehová), A.C. and T.Y. (F. Rey). Pterin analyses in urine were performed by two-dimensional high-voltage electrophoresis/paper chromatography as well as by gas chromatography-mass spectrometry. The trimethylsilyl derivatives were analyzed by gas chromatography on a 20 m OV-l glass capillary column and detected by a nitrogen detector as well as by mass fragmentography at m/e 409. Mass spectra were identical with those of the pure reference compounds. All three patients excreted high amounts of neopterin and smaller quantities of dihydroxanthopterin in urine but no biopterin or dihydrobiopterin. This pterin pattern was the same as in the first two patients (M.K. and Z.Y.) shown to suffer from dihydrobiopterin synthetase deficiency (A. Niederwieser et al. Lancet I: 131, 1979; H.-Ch. Curtius et al. Clin. Chim. Acta 93: 251, 1979). Neopterin was shown to be of D-erythro and not of threo configuration. Furthermore, the patients' elevated serum phenylalanine level was normalized by oral administration of L-erythro-tetrahydrobiopterin bishydrochloride, 2.5 mg/kg body weight. Conclusion: Analysis of urinary pterins is of value for the early detection of atypical PKU and - in combination with pterin administration tests - for the localization of the corresponding enzyme defect.