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The phenylalanine response curve in relation to growth and mental development in the first year of life
L W van der Schot1, W H Doesburg, R C Sengers
1Department of Medical Psychology, University Hospital Nijmegen, The Netherlands.
Insights
Early treatment of phenylketonuria (PKU) in children is crucial. Maintaining phenylalanine levels below 0.5 mmol/l is associated with better cognitive outcomes, preventing developmental delays.
Area of Science:
- Pediatric Endocrinology
- Metabolic Disorders
- Neurodevelopmental Pediatrics
Background:
- Phenylketonuria (PKU) is a genetic metabolic disorder requiring early intervention.
- Dietary management aims to control phenylalanine levels to prevent neurological damage.
- Long-term effects of phenylalanine control on growth and cognitive development require ongoing study.
Purpose of the Study:
- To evaluate the impact of early treatment for classical phenylketonuria on growth and mental development.
- To investigate the relationship between phenylalanine concentrations and developmental outcomes in treated children.
- To establish optimal phenylalanine level targets for neurodevelopmental preservation.
Main Methods:
- Thirty-three children with classical PKU were treated from 9-21 days of age.
- Phenylalanine concentrations were monitored regularly and plotted on response curves.
- Growth parameters (weight, height, head circumference) and mental development indices were assessed at 1 and 2 years of age.
Main Results:
- Growth measurements were normal at 1 month, declined at 1 year, and normalized by 2 years, independent of phenylalanine levels.
- Mental development indices were generally within normal ranges at 1 and 2 years.
- Significant negative correlations were observed between mental development at 1 year and phenylalanine levels >0.5 mmol/l; changes in development between years 1 and 2 correlated with second-year phenylalanine levels.
Conclusions:
- While early PKU treatment supports normal growth, maintaining phenylalanine levels below 0.5 mmol/l is critical for optimal cognitive development.
- Elevated phenylalanine levels, particularly in the second year of life, are associated with poorer neurodevelopmental trajectories.
- The findings underscore the importance of stringent phenylalanine control throughout early childhood for preventing cognitive deficits in PKU.
Abstract:
Thirty-three children with classical phenylketonuria were treated from 9 to 21 days of age onward. The standard for phenylalanine concentration was 0.2-0.5 mmol/l. During the first years of life phenylalanine concentrations were measured once every two to six weeks. For each child these values were graphically plotted in a so-called phenylalanine response curve. Growth and mental development indices were assessed at about one and two years of age. Measurements for weight, height and head circumference were normal at one month of age, showed a significant decline at the age of one year but were restored for normal values at the age of two. No associations were found with phenylalanine parameters. Mental development indices at one and two years were not different from normal. Significant negative correlations were found between mental development indices at one year and phenylalanine values above 0.5 mmol/l. Changes in mental development indices between the first and second years of life are significantly related to the phenylalanine levels during the second year of life.