Which metabolic disorder is most commonly screened and can affect neurodevelopment if untreated?

• A. Phenylketonuria (PKU)
• B. Cystinuria
• C. Homocystinuria
• D. Tyrosinemia

Answer: (A)

Screening newborns for metabolic disorders targets conditions that, if not identified and treated early, can lead to neurodevelopmental problems. Phenylketonuria is the classic example because a deficiency of phenylalanine hydroxylase lets phenylalanine build up in the blood and brain. That buildup, if not controlled from infancy, causes intellectual disability and other neurodevelopmental impairments. Detecting elevated phenylalanine through routine newborn screening enables immediate dietary management to restrict phenylalanine and prevent brain injury, which is why this condition is the most commonly screened and most strongly linked to neurodevelopmental outcomes when untreated. The other disorders listed have health impacts, but they don’t carry the same universal newborn-screening emphasis for preventing neurodevelopmental delay.