Treatment of classic D low phenylalanine diet Duration of treatment: It is advocated that the child should be treated at least until pubertal maturity, preferably for life, with appropriate relaxation of dietary restrictions in adulthood.
Treatment principles: 1. Phenylalanine intake must ensure the minimum requirements for growth and metabolism. Due to the lack of phenylalanine hydroxylase in the patient’s liver, phenylalanine cannot be metabolized normally to generate tyrosine and accumulates in the blood in large quantities, causing neurological damage, and phenylalanine is metabolized by bypass to generate phenyl pyruvate and phenylacetic acid, which is excreted in large quantities through urine, so the patient’s urine has a special unpleasant rat smell. At the same time, phenylalanine is an essential amino acid for growth and development, and insufficient supply will also lead to growth retardation, which can seriously lead to death. Therefore, phenylalanine should neither be consumed too much nor too little.
2. On the other hand, since natural protein contains 4-6% phenylalanine, it is necessary to control the intake of natural protein and use low or no phenylalanine milk powder or protein powder as the main source of protein for the children, and to ensure that sufficient calories are given.
3.Breast milk is still the best diet for breastfed children, and giving calculated amounts of breast milk is very beneficial to the development of the affected children, so never stop breastfeeding.
4. Individual differences must be considered. Since the degree of defective phenylalanine hydroxylase activity in children varies greatly, dietary treatment should adhere to the principle of individualization, and because of the differences in protein, calorie and phenylalanine needs and tolerance of children of all ages, recipes should be formulated and adjusted according to the age, weight and blood concentration of each child, so that the blood phenylalanine concentration is controlled at an appropriate level.
5, food contains protein except fat and sugar; among them, phenylalanine content accounts for 3%D5% of protein. Therefore, it is difficult to eliminate phenylalanine from common foods.
(1) Low or no phenylalanine milk powder, protein powder, starch and beverages can be used, and such low-phenylalanine food feeding is supplemented with breast milk and milk or other supplementary food.
(2) To ensure the efficacy of the treatment, blood phenylalanine concentration should be monitored regularly. Normal blood phenylalanine concentration is 1-2mg/dl, typical phenylalanine blood concentration without treatment is >20mg/dl, mostly between 20-50mg/dl, >50mg/dl is rare. Blood Phe concentration monitoring should be repeated once or twice a week for the first month after dietary therapy and once a month thereafter. Blood amino acid analysis should be performed if necessary to determine tyrosine level, ratio of branched chain amino acids to aromatic amino acids, etc.
(3) For atypical phenylketonuria, in addition to dietary treatment, a variety of neuromediators should be supplemented, such as tetrahydrobiopterin (BH4), dopa, 5-hydroxytryptamine, folic acid, etc.
(4) Children with other comorbidities should be treated symptomatically. For example, children with seizures should be treated with regular antiepileptic drugs as early as possible. Children with eczema may heal spontaneously after satisfactory control of blood Phe concentrations. If eczema is severe, topical medications may be given for symptomatic treatment.
(5) Enzyme therapy and gene therapy PKU is an enzyme-deficient disease, and enzyme replacement therapy is certainly an ideal treatment method, but enzyme preparations with therapeutic value have not yet been found due to limitations in safety, stability, and rejection reactions. Theoretically, correction of defective genes through gene therapy is the fundamental way to treat PKU. However, gene therapy for PKU is at the stage of animal experiments and is still quite far from the clinic.