Phenylketonuria

Alternative Names

PKU; Neonatal phenylketonuria

Definition of Phenylketonuria

Phenylketonuria (PKU) is a rare condition in which a baby is born without the ability to properly break down an amino acid called phenylalanine.

Causes, incidence, and risk factors

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.

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.

Signs and tests

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.

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.

Expectations (prognosis)

The outcome is expected to be very good if the diet is closely followed, starting shortly after the child’s birth. If treatment is delayed or the condition remains untreated, brain damage will occur. School functioning may be mildly impaired.

Review

Benjamin W. Van Voorhees, MD, MPH, Assistant Professor of Medicine, Pediatrics and Psychiatry, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 5/27/2009

Phenylketonuria test
Phenylketonuria test

ADAM Medical Encyclopedia

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