A newborn screening test returns positive for phenylketonuria (PKU). The infant is currently being breastfed and is clinically well. Serum phenylalanine is 24 mg/dL. What is the MOST appropriate initial management?
- A Start phenylalanine-free formula while allowing LIMITED continued breastfeeding, monitoring serum phenylalanine levels ✓
- B Completely stop breastfeeding and start phenylalanine-free formula exclusively
- C Start oral sapropterin (BH4) immediately without dietary modification
- D Start high-protein formula to compete with phenylalanine at the BBB
Explanation
Current PKU management guidelines favor a combined approach: phenylalanine-free amino acid formula provides safe protein intake while LIMITED breastfeeding (with frequent serum Phe monitoring) is allowed because breast milk has lower phenylalanine content (~45 mg/dL) compared to cow's milk formula, and breastfeeding provides immunological and developmental benefits. Complete cessation of breastfeeding is unnecessary. Sapropterin (BH4 cofactor) is effective for BH4-responsive PKU (typically mild/moderate forms, phenylalanine hydroxylase variants) but response must be tested and diet is still needed. Target serum Phe is 2–6 mg/dL in infants.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.