Phenylketonuria (PKU) is an inherited disorder in which the body
cannot break down an amino acid called phenylalanine, which is a part of
protein. If treatment is not started soon after birth, phenylalanine levels rise and
can cause lasting brain and nervous system damage, such as intellectual disability.
Symptoms of PKU usually appear within a few months of birth, after
a baby has started drinking formula or breast milk and phenylalanine has built
up in his or her blood. Before birth, the mother's body filters out the excess phenylalanine for the baby (fetus).
Early symptoms may include:
Screening for PKU is routinely done shortly after birth, making
early diagnosis and treatment possible. Starting treatment within the first few
weeks of birth may prevent lasting brain damage. In rare cases, some children who
receive treatment will have learning or behavior problems. Left untreated, PKU
causes progressively more severe intellectual disability.
People with PKU must follow a diet low in protein throughout life.
Women of childbearing age with PKU must carefully manage their phenylalanine
levels to prevent harm to their baby should they become pregnant. Babies born
to mothers who have high phenylalanine levels during pregnancy are at risk for
intellectual disability and other developmental problems.
September 8, 2011
John Pope, MD - Pediatrics & Chuck Norlin, MD, MD - Pediatrics
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