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Phenylketonuria — RACP Paediatrics MCQ

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ModerateGenetics and metabolicPhenylketonuriaRACP Paediatrics

A newborn bloodspot screen reports markedly elevated phenylalanine. The baby is feeding well and examination is normal. Confirmatory plasma amino acids support classic phenylketonuria. What is the most appropriate management?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Start a phenylalanine-restricted diet with metabolic specialist supervision

PKU is often asymptomatic at birth but untreated hyperphenylalaninaemia causes irreversible neurodevelopmental injury; early dietary treatment is essential. High-protein feeds would increase phenylalanine load. The pearl is that newborn screening is designed to detect treatable conditions before clinical signs appear.

Reference: Australian Newborn Bloodspot Screening Programme; Therapeutic Guidelines (eTG)