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Rethinking phenylalanine levels in phenylketonuria for optimal neurocognitive development beyond childhood
Beatriz Câmara1, Cristina Florindo2, Cláudia Bandeira de Lima3
1Pediatric Department, Funchal Central Hospital, SESARAM-EPERAM, Funchal, Portugal.
Frontiers in Pediatrics
|July 4, 2025
Summary
Phenylketonuria (PKU) management is crucial for cognitive function. Elevated phenylalanine (Phe) levels in adolescents with PKU negatively impact executive functions, emphasizing the need for strict dietary adherence.
Area of Science:
- Biochemistry
- Neuroscience
- Pediatrics
Background:
- Phenylketonuria (PKU) is an inherited metabolic disorder affecting phenylalanine (Phe) processing.
- While early intervention improves outcomes, neurocognitive deficits persist in adolescents with PKU.
- Current metabolic control guidelines for PKU patients over 12 years vary between the EU and US.
Purpose of the Study:
- To investigate the association between blood Phe levels and cognitive functions (IQ, executive functions) in adolescents with PKU.
- To evaluate the impact of dietary adherence on cognitive outcomes in this population.
Main Methods:
- Longitudinal monitoring of blood Phe levels using the Index of Dietary Control (IDC).
- Cognitive assessments included the Wechsler Intelligence Scale for Children-Third Edition and the d2 Test of Attention.
- Study included 14 early-treated PKU patients aged 12-17 years.
Main Results:
- Good metabolic control (IDC <360 µM) before age 12 correlated with higher IQ.
- Adolescents with PKU noncompliant with diet showed declining attentional performance after age 12.
- Elevated Phe levels at cognitive assessment were linked to poorer performance.
Conclusions:
- Elevated Phe levels detrimentally affect executive functions in adolescent PKU patients.
- Further research is needed to establish safe Phe level ranges for individuals over 12 years old.
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