If an Infant Is Found to Have Hyperphenylalaninemia Based on a Newborn

question 1

Multiple Choice

If an infant is found to have hyperphenylalaninemia based on a newborn screen, but this defect doesn't respond to a low phenylalanine diet, what type of molecular defect would be suspected?

• A) Null mutation for phenylalanine hydroxylase
• B) Dominant negative mutation for phenylalanine hydroxylase
• C) A defect in tetrahydrobiopterin (BH₄) metabolism
• D) A mutation in tyrosine hydroxylase
• E) A mutation in tryptophan hydroxylase

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