[Phenylketonuria yesterday and today. Evaluation of the work of systematic neonatal screening]

Phenylketonuria is due in the very great majority of cases to a deficiency in phenylalanine hydroxylase, an enzyme whose cofactor is biopterin. Prenatal screening consists in measuring the concentration of phenylalanine in a sample of dried blood taken after birth (levels are already raised by day 3). Screening, organized by the Association française pour le dépistage et la prévention des handicaps de l'enfant, is very thorough (cover greater than 99%). Treatment involves observance of dietary restriction for at least five years. Results are good. Questions concerning the useful duration of dietary treatment, the level of phenylalanine that should not be exceeded, and the future of girls with PKU remain controversial. When adult, such girls may give birth to retarded children if they do not resume dietary restriction before becoming pregnant. Now that problems of screening, its organization, and the management of diet have been solved, these questions are the new challenge that faces us.