Question
During newborn screening, a PA value of 121 was found, suspected of being phenylketonuria. What is the normal range for phenylketonuria?
Answer
Newborns may experience transient hyperphenylalaninemia, which is related to enzyme activity and usually gradually returns to normal. For the screening of phenylketonuria, if the serum phenylalanine level in the child exceeds 1.2 mmol/L (20 mg/dl), it can be considered a confirmed diagnosis. Early clinical manifestations may include yellowing of the hair and whitening of the skin, but these are non-specific.