Suspected pterin-4a-carbinolamine dehydratase deficiency : hyperphenylalaninaemia due to inhibition of phenylalanine hydroxylase by tetrahydro-7-biopterin

A new form of atypical phenylketonuria coupled with a transient hyperphenylalaninaemia has recently been discovered. The new metabolic disorder is characterized by an accompanying excretion of 7-substituted pterins, i.e. 7-biopterin (primapterin), 6-oxo-7-biopterin and 7-neopterin (anapterin) in the patients' urine (Curtius et al 1988; Dhondt et al 1988). This excretion of 7-substituted pterins appears to be associated with an enzyme defect in the aromatic amino acid hydroxylating system