Question
Patient Gender: Male, Age. Main Symptoms: Low intelligence, seizures during fever, unclear speech. Onset Time: 1 and a half years old. Laboratory Test Results: Urinalysis shows mild ketonuria.
Answer
A low phenylalanine diet is primarily suitable for patients with typical PKU and those with blood phenylalanine levels consistently higher than 1.22 mmol/L (20 mg/dl). Since phenylalanine is an essential amino acid for protein synthesis, its complete deficiency can also lead to neurological damage. Therefore, infants can be fed a specially formulated low-phenylalanine milk powder, and during the addition of complementary foods in early childhood, low-protein foods such as starches, vegetables, and fruits should be the mainstay. The required amount of phenylalanine is approximately 50-70 mg/(kg.d) for infants under 2 months old, about 40 mg/(kg.d) from 3 to 6 months, and an average of 25-30 mg/(kg.d) by the age of 2. For children over 4 years old, it is about 10-30 mg/(kg.d), aiming to maintain blood phenylalanine concentrations between 0.12-0.6 mmol/L (2-10 mg/dl). Dietary control should be maintained at least until after puberty. Beijing children’s hospitals, research institutes, and women’s and children’s hospitals are capable of conducting this type of examination. Once diagnosed, low-phenylalanine dietary treatment and symptomatic management are the first steps.