Patient's question:
A newborn baby discovered phenylketonuria at 14 days and has not been treated yet.Doctor's answer:
Hello! Phenylketonuria (PKU) is caused by abnormal phenylalanine metabolism in the body. Phenylalanine is an essential amino acid required for human growth and metabolism. The activity of phenylalanine hydroxylase, an enzyme that converts phenylalanine to tyrosine, requires tetrahydrobiopterin (BH4) as a cofactor for optimal function. A reduction in phenylalanine hydroxylase activity or a deficiency in BH4 can prevent phenylalanine from being converted to tyrosine, leading to a significant increase in phenylalanine and its byproduct metabolites—phenylpyruvate, phenylacetic acid, and phenyllactic acid—which can cause brain damage and result in the onset of the disease.If children with PKU are not treated or treatment is delayed, most will experience delays in intellectual, motor, and language development. However, if diagnosed and treated before symptoms appear—such as PKU detected through newborn screening—early intervention allows nearly 90% of children to achieve normal intelligence. Only a small portion may still experience intellectual decline due to poor treatment compliance or severe conditions, resulting in poor control of blood phenylalanine levels.
Medical Advice:
Hello! The treatment for PKU requires targeted measures based on its classification. First, determine the classification and then administer appropriate medication. Generally, the recommended blood phenylalanine range is as follows:
- 0–3 years: 120–240 μmol/L
- 3–8 years: 180–360 μmol/L
- 8–13 years: 180–480 μmol/L
- 13–18 years: 180–600 μmol/L
- >18 years: 180–900 μmol/L
PKU is a genetic metabolic disorder and cannot be cured. For families with a child already diagnosed with PKU, if the parents wish to have another child, prenatal diagnosis can determine whether the fetus is affected by the condition.