Inborn error of metabolism: Individuals with phenylketonuria (PKU) avoid severe neurocognitive impairment if which dietary intervention is implemented early and consistently?

Difficulty: Easy

Correct Answer: phenylalanine in the diet is restricted

Explanation:


Introduction / Context:
PKU is a classic example of how genetics and nutrition intersect. Without treatment, accumulation of phenylalanine and its metabolites damages the developing brain. Early detection and dietary management prevent severe outcomes.



Given Data / Assumptions:

  • PKU results from deficient phenylalanine hydroxylase activity.
  • Untreated PKU leads to high phenylalanine levels and neurotoxicity.
  • Newborn screening enables prompt dietary intervention.



Concept / Approach:
The therapeutic goal is to keep blood phenylalanine in a safe range by restricting dietary phenylalanine, found in high-protein foods and aspartame. Tyrosine becomes conditionally essential and is supplemented. Lifelong adherence optimizes cognitive outcomes.



Step-by-Step Solution:
Identify toxic substrate: phenylalanine accumulation causes harm.Treatment principle: substrate restriction and product supplementation (tyrosine).Implement low-phenylalanine diet; avoid aspartame; use medical formulas.Thus the correct intervention is phenylalanine restriction.



Verification / Alternative check:
Clinical studies show normalized development when dietary Phe is controlled from infancy. Elevated phenylalanine correlates with poorer IQ and executive function.



Why Other Options Are Wrong:

  • Tyrosine restriction: counterproductive; tyrosine is often supplemented.
  • Homogentisic acid restriction: pertains to alkaptonuria, not PKU.
  • None of the above: incorrect because Phe restriction is effective.



Common Pitfalls:
Assuming diet can be liberalized in adulthood; evidence supports lifelong management. Hidden Phe sources (sweeteners) can be overlooked.



Final Answer:
phenylalanine in the diet is restricted

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