RT Journal Article SR Electronic T1 Biopterin derivatives in normal and phenylketonuric patients after oral loads of L-phenylalanine, L-tyrosine, and L-tryptophan. JF Archives of Disease in Childhood JO Arch Dis Child FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP 771 OP 777 DO 10.1136/adc.51.10.771 VO 51 IS 10 A1 R J Leeming A1 J A Blair A1 A Green A1 D N Raine YR 1976 UL http://adc.bmj.com/content/51/10/771.abstract AB Plasma biopterin derivatives studied in 10 normal and 21 phenylketonuric children showed a significantly high concentration in the latter group. Biopterin derivatives correlated with plasma phenylalanine concentration, but in normal adults given an oral phenylalanine load the rate of increase with phenylalanine differed from that in phenylketonuric patients. A patient with hyperphenylalaninaemia, not due to phenylketonuria, had an abnormal biopterin derivatives response to phenylalanine distinct from that of patients with classical phenylketonuria. This may be a useful investigation to differentiate some variants of phenylketonuria.