Abstract
Atypical forms of phenylketonuria (PKU) are associated with defects in the synthesis or regeneration of the biopterin cofactors. In order to prevent irreversible neurological damage, patients with hyperphenylalaninemia are being screened for biopterin. A newborn male was found to have 34.4 mg/dl of phenylalanine on the 7th day of life. Dietary therapy for PKU was begun and at the age of 19 days urine biopterin levels were analyzed by the method of Fukushima and Nixon (Anal.Bioch. 102, 177, 1980). Urine neopterin (N) was 879 ng/ml and biopterin (B) 142 ng/ml with an abnormal ratio of N/B of 6.2 (normal ≤ 2).Urine biopterin determination was repeated on the 28th day of life and at this time N was 2155 ng/ml and B was 605 ng/ml, N/B 3.6. A week later the baby's urine was examined again and the ratio of N/B was 3.0. Because of the abnormal ratio of N/B, challenge with L-tetrahydrobiopterin, 2 mg/Kg, was given orally with no effect on blood phenylalanine which remained at 18 mg/dl after 4 and 6 hours. At 40 days of age urine biopterin approached normal values and N/B was 1.3. These findings suggest a transient form of biopterin synthetase deficiency not previously reported. In newborns with hyperphenylalaninemia where abnormal ratio of N/B is found, repeated determinations are needed in order to avoid a false diagnosis of atypical PKU.
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Matalon, R., Michals, K., Lee, CL. et al. 739 TRANSIENT BIOPTERIN SYNTHETASE DEFICIENCY IN A NEW-BORN WITH PHENYLKETONURIA. Pediatr Res 15 (Suppl 4), 565 (1981). https://doi.org/10.1203/00006450-198104001-00762
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DOI: https://doi.org/10.1203/00006450-198104001-00762
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