pediatrics
Phenylketonuria (PKU)
Treatment of PKU
Dietary phenylalanine restriction Treatment of phenylketonuria is lifelong dietary phenylalanine restriction. All natural protein contains about 4% phenylalanine. Therefore dietary staples include Low-protein natural foods (eg, fruits, vegetables, certain cereals) Protein hydrolysates treated to remove phenylalanine Phenylalanine-free elemental amino acid mixtures Examples of commercially available phenylalanine-free products include PKU Anamix®(for infants), XPhe Maxamaid®(for children 1 to 8 years), XP Maxamum®(for children>8 years); Phenex®-1 and Phenex®-2; Phenyl-Free®1 and Phenyl-Free®2; PhenylAde®(varieties); PKU Lophlex®LQ; and Phlexy-10®(multiple formulations). Some phenylalanine is required for growth and metabolism; this requirement is met by measured quantities of natural protein from milk or low-protein foods. Frequent monitoring of plasma phenylalanine levels is required; recommended targets for all children are between 2 mg/dL and 6 mg/dL (120 to 360 micromol/L). Dietary planning and management need to be initiated in women of childbearing age before pregnancy to ensure a good outcome for the child. Tyrosine supplementation is increasingly used because it is an essential amino acid in patients with PKU. In addition, all patients with phenylalanine hydroxylase deficiency should be given a trial ofsapropterinto determine benefit. For those with BH4 deficiency, treatment also includes tetrahydrobiopterin 1 to 5 mg/kg orally 3 times a day;levodopa,carbidopa, and 5-OHtryptophan; and folinic acid 10 to 20 mg orally once a day in cases of dihydropteridine reductase deficiency. However, treatment goals and approach are the same as those for PKU. 