[Neuropsychological follow-up of children with phenylketonuria treated early].

We evaluated, yearly, the neuro-psychological development in 16 out of the 27 children with phenylketonuria detected via neonatal screening in the years 1980-90. 14 children had the classical form, while 2 had "variant" type of phenylketonuria. Development quotients always were slightly lower in patients than in controls, but the greatest difference was seen at 1 year of age (92.5 +/- 6.7 vs 101.6 +/- 2.2). At age 6 years, 4 children out of 11 had a IQ equal or below 90.2 of them had neonatal asphyxia, while the others showed, after age 2-4, constantly elevated phenylalanine levels. Four children had a bad metabolic control, as from the age of 2-4 year, and only 1 of them showed a normal IQ at 6 years of age. Regression analyses were used to determine the best predictors of IQ. Parents' social level stood out as the best predictor of IQ at 6 years of age. If this parameter was excluded, phenylalanine level, especially at age 4, best predicted IQ. The following variables had no influence: age at start of diet (they were all begun on diet within the first month of life), pre-diet phenylalanine levels and phenylalanine levels at 1 year of age (all children were, at this age, on good control), DQ (Development Quotient) at age 1. A high percentage (10 out 14) of hyperactive and psychologically instable children was also found, but with no correlations with IQ levels.