Patient's question:
Currently being treated, already 4 years old.Doctor's answer:
Phenylketonuria (PKU) is a common amino acid metabolic disorder caused by a deficiency in enzymes of the phenylalanine metabolic pathway, which prevents phenylalanine from being converted into tyrosine. This leads to the accumulation of phenylalanine and its ketone bodies, which are excreted in large amounts in the urine. Clinical manifestations primarily include intellectual disability, recurrent seizures, and hypopigmentation.Recommendations: Once diagnosis is confirmed, active treatment should be initiated as early as possible, primarily through dietary therapy. The earlier treatment begins, the better the outcome.
1. Low-phenylalanine diet is mainly suitable for typical PKU patients and those with persistently elevated blood phenylalanine levels (above 1.22 mmol/L or 20 mg/dL). Since phenylalanine is an essential amino acid for protein synthesis, complete deficiency can also cause neurological damage. Therefore, infants can be fed specially formulated low-phenylalanine formula milk, and during weaning, starchy foods, vegetables, and fruits with low protein content should be prioritized.
Phenylalanine requirements:
- Up to 2 months: ~50–70 mg/(kg·d)
- 3–6 months: ~40 mg/(kg·d)
- 2 years: ~25–30 mg/(kg·d)
- Over 4 years: ~10–30 mg/(kg·d)
The goal is to maintain blood phenylalanine levels between 0.12–0.6 mmol/L (2–10 mg/dL). Dietary control should be maintained at least until after puberty.
2. BH4, 5-hydroxytryptamine, and L-DOPA are primarily used for BH4-deficient PKU. In addition to dietary control, these medications must be administered.
Lifestyle care:
- Avoid consanguineous marriage.
- Implement newborn screening to detect the condition early and initiate treatment promptly.
- Pregnant women with a family history of this disease must undergo prenatal diagnosis using DNA analysis or amniotic fluid tryptophan testing.