Metabolism

Phenylketonuria

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Phenylketonuria, PKU

  • Epidemiology
  1. Incidence: 1:15000
  • Pathophysiology
  1. Autosomal-recessive disorder
  2. Phenylalanine hydroxylase gene mutation
    1. Enzyme converts phenylalanine to tyrosine
    2. Phenylalanine concentrations rise with mutation
  3. Phenylalanine threshold for adverse effects >20 mg/dl
  • Symptoms
  1. Irritability
  • Signs
  • Complications on unrestricted diet
  1. Head Circumference small for age (Microcephaly)
  2. Cognitive delay
  3. Light skin pigmention
  • Labs
  1. Identified on Newborn Screen
  • Management
  1. Strict low phenylalanine diet for life
    1. Infant: Low Phenylalanine formula
    2. Pregnancy: Monitor phenylalanine concentrations
  2. Supplementation
    1. Tyrosine 25 mg/kg/day
    2. Amino acid dosing
      1. Infant: 3 g/kg/day
      2. Child: 2 g/kg/day