What developmental risk is associated with prolonged low blood phenylalanine and tyrosine levels during infancy while taking sapropterin dihydrochloride?

Prolonged low blood phenylalanine and tyrosine levels during infancy while taking sapropterin dihydrochloride are associated with impaired neurodevelopmental outcomes, requiring active management of dietary phenylalanine and overall protein intake to maintain adequate blood levels and nutritional balance.