Phenylketonuria

Cards (7)

  • IX. PHENYLKETONURIA
    PKU is a disease of metabolism inherited as an autosomal recessive trait
    ● LAST THREE DISEASES: Phenylketonuria (PKU), Maple Syrup Urine Disease (MSUD), and Galactosemia are all problems of different liver enzymes.
    ● Cause: absence of the liver enzyme phenylalanine hydroxylase, which prevents conversion of phenylalanine into tyrosine
  • Phenylalanine: an essential amino acid from protein foods that we eat. It must be converted into tyrosine as shown in the photo.
    ○ Tyrosine: a precursor of epinephrine,
    ○ Thyroxine & Melanin for the body to use because in PKU there is no converting enzyme.
    ● Because in PKU there is no converting enzyme, excessive phenylalanine builds up in the body, causing permanent damage to brain tissue and leaving children severely cognitively challenged.
  • ASSESSMENT
    ● PKU cannot be detected prenatally because phenylalanine level does not rise in utero
    ○ Only rises as children breastfeed from taking up protein so screening for it may be done 2-3 days after birth when the newborn has breastfed already. This is included in the newborn screening program.
    ● Normal phenylalanine in blood is less 2 mg/dL.
    ○ More than 4mg/dL: high and may mean PKU
    8mg/dL and above: toxic to the brain
    1. Musty or mousy urine odor
    Phenyl Pyruvic Acid: breakdown product of phenylalanine
    ○ This acid spills into the urine which sometimes pervades not only in the urine but in the entire child’s odor.
    2. Fair skinned, light blonde hair, and blue eyes
    Tyrosine is necessary for building body pigment and is incorporated into thyroxine. Without it, the body pigments fades.
    3. Fails to meet average growth standards
    ● Because of lack of thyroxine production from metabolism.
  • 4. Skin prone to eczema
    ● There is a strong association between children with PKU and atopic dermatitis
    5. Low IQ of 20 or less, seizures, and muscular hypertonicity and spasticity
    ● This is the goal of prevention of PKU, to prevent cognitive damage as phenylalanine is toxic to the brain.
  • MANAGEMENT
    1. Place child on formula extremely low in phenylalanine, such as Lofenalac.
    ● A small amount of milk may be added or limited breast feeding is also allowed so child still can receive some phenylalanine necessary for growth and repair of body cells but not too high.
    2. As children grow older and have solid foods added to their meals, these foods also must be low in phenylalanine. It includes orange juice, bananas, potatoes, lettuce, spinach, and peas.
    ● Avoid foods highest in phenylalanine those that are rich in protein, such as meats, eggs, and milk, indefinitely or for life
  • 3. Children need their blood and urine monitored frequently for phenylalanine levels.
    ● Make it sure it does not reach 8 mg/dL.
    4. Hemoglobin levels should also be closely monitored to ensure that the child is not becoming anemic, because iron is found primarily in protein-rich foods, which the child must avoid
    ● If such cases and there is anemia, the child may be given ferrous sulphate.