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Inborn Errors of Metabolism · USMLE Step 1

Why do many amino acid–metabolism IEMs result in neurologic deficits if untreated early in life?

  1. Because amino acids serve as the main energy source for neurons
  2. Because toxic amino acids or metabolites damage developing brain tissue
  3. Because amino acids are entirely unable to cross the blood-brain barrier
  4. Because they trigger massive lactic acidosis that selectively kills neurons
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Correct answer: Because toxic amino acids or metabolites damage developing brain tissue

Toxic accumulation of amino acids or their metabolites can disrupt neurotransmitter balance or damage neural tissue — leading to developmental delay, intellectual disability or seizures seen in untreated amino acidopathies.

Difficulty: Medium Question 16 of 19

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