Tuesday, October 5, 2010

Phenylketonuria

DEFINITION
Phenylketonuria (fen-ul-ke-toe-NU-re-uh) is a birth defect in which a mutation occurs in a gene containing instructions for making the enzyme needed to break down the amino acid phenylalanine.
Amino acids are the building blocks for protein, but too much phenylalanine can cause a variety of health problems. People with phenylketonuria (PKU) — babies, children and adults — need to follow a diet that limits phenylalanine, which is found mostly in high-protein foods.
Babies in the United States and many other countries are screened for phenylketonuria soon after birth. Although phenylketonuria is rare, recognizing phenylketonuria right away can help prevent serious health problems.

CAUSES
Phenylketonuria (PKU) is inherited, which means it is passed down through families. Both parents must pass on the defective gene in order for a baby to have the condition. This is called an autosomal recessive trait.
Babies with PKU are missing an enzyme called phenylalanine hydroxylase, which is needed to break down an essential amino acid called phenylalanine. The substance is found in foods that contain protein.
Without the enzyme, levels of phenylalanine and two closely-related substances build up in the body. These substances are harmful to the central nervous system and cause brain damage.


SYMPTOMS
Phenylalanine plays a role in the body's production of melanin, the pigment responsible for skin and hair color. Therefore, infants with the condition often have lighter skin, hair, and eyes than brothers or sisters without the disease.
Other symptoms may include:
  • Delayed mental and social skills
  • Head size significantly below normal
  • Hyperactivity
  • Jerking movements of the arms or legs
  • Mental retardation
  • Seizures
  • Skin rashes
  • Tremors
  • Unusual positioning of hands
If the condition is untreated or foods containing phenylalanine are not avoided, a "mousy" or "musty" odor may be detected on the breath and skin and in urine. The unusual odor is due to a build up of phenylalanine substances in the body.

EXAMS@TEST
PKU can be easily detected with a simple blood test. Most states require a PKU screening test for all newborns. The test is generally done with a heelstick shortly after birth.
If the initial screening test is positive, further blood and urine tests are required to confirm the diagnosis.

TREATMENT
PKU is a treatable disease. Treatment involves a diet that is extremely low in phenylalanine, particularly when the child is growing. The diet must be strictly followed. This requires close supervision by a registered dietitian or doctor, and cooperation of the parent and child. Those who continue the diet into adulthood have better physical and mental health. “Diet for life” has become the standard recommended by most experts. This is especially important before conception and throughout pregnancy.
Phenylalanine occurs in significant amounts in milk, eggs, and other common foods. The artificial sweetener NutraSweet (aspartame) also contains phenylalanine. Any products containing aspartame should be avoided.
A special infant formula called Lofenalac is made for infants with PKU. It can be used throughout life as a protein source that is extremely low in phenylalanine and balanced for the remaining essential amino acids.
Taking supplements such as fish oil to replace the long chain fatty acids missing from a standard phenylalanine-free diet may help improve neurologic development, including fine motor coordination. Other specific supplements, such as iron or carnitine, may be needed.

http://www.youtube.com/watch?v=1gaDFPOn-mw&feature=related

http://health.nytimes.com/health/guides/disease/phenylketonuria/overview.html


http://www.mayoclinic.com/health/phenylketonuria/DS00514


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