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Correlation of age-specific phenylalanine levels with intellectual outcome in patients with phenylketonuria

Krista S Viau1, Heidi J Wengreen, Sharon L Ernst

  • 1Department Pediatrics, University of Utah, Salt Lake City, UT, USA. krista.viau@hsc.utah.edu

Journal of Inherited Metabolic Disease
|May 11, 2011
PubMed

Insights

Early blood phenylalanine (Phe) control in phenylketonuria (PKU) is crucial. Lower Phe levels from birth to 12 years improve cognitive outcomes, particularly verbal comprehension and perceptual reasoning.

Area of Science:

  • Metabolic Disorders
  • Neurodevelopmental Pediatrics
  • Clinical Genetics

Background:

  • Phenylketonuria (PKU) is a genetic disorder requiring lifelong dietary management.
  • Treated PKU patients may exhibit subtle neurocognitive deficits.
  • Blood phenylalanine (Phe) levels are a key indicator of treatment efficacy.

Purpose of the Study:

  • To investigate the association between blood Phe levels during specific developmental periods and intellectual outcomes in treated PKU patients.
  • To assess the impact of Phe concentration and variation on cognitive functions.
  • To determine the influence of age on the relationship between Phe control and neurodevelopment.

Main Methods:

  • Retrospective analysis of data from 55 PKU patients at the University of Utah Metabolic Clinic.
  • Evaluation of intellectual outcomes using measures of verbal comprehension, perceptual reasoning, and processing speed.
  • Linear regression analysis to correlate blood Phe levels (concentration and variation) with cognitive assessments across different age groups (0-6, 7-12, >12 years).

Main Results:

  • Higher yearly median blood Phe levels from 0-6 and 7-12 years were inversely associated with perceptual reasoning.
  • Elevated Phe concentrations in early childhood (0-6 years) negatively impacted verbal comprehension (p = 0.001).
  • Phe level variation did not significantly affect intelligence, but was linked to pretreatment and median Phe levels. Frequent monitoring from 7-12 years reduced high Phe levels.

Conclusions:

  • Blood Phe concentration during the first 12 years of life significantly impacts verbal comprehension and perceptual reasoning in PKU patients.
  • Treatment compliance, affecting Phe levels, is critical for neurocognitive development, especially in early life.
  • Long-term cognitive outcomes in PKU are closely tied to maintaining optimal Phe control during key developmental windows.

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