What is phenylketonuria (PKU)?
(PKU) is a rare
genetic disorder in which the body cannot break down
an amino acid called phenylalanine (say "fehn-uhl-AL-uh-neen"), which is a part of protein. This substance is found in breast milk, many types of baby formula, and most foods, especially those with a lot of protein, such as meat, eggs, and dairy products. If PKU is not treated, phenylalanine can build up in the blood and lead to intellectual disability and problems with the central nervous system (brain and spinal cord).
The good news is that early treatment can prevent all or most problems. Babies born with PKU need to start treatment with special formula soon after birth.
What causes PKU?
PKU is passed down through
families. To have the disease, a baby must get the
gene from both parents. If a baby gets the gene from
only one parent, he or she is a
carrier of the PKU gene but does not have the
If you have a child with PKU and are thinking about having another baby, you may want to get genetic counseling. If you have a family history of PKU, talk with your doctor about genetic testing if you want to find out whether you carry the gene.
What are the symptoms?
If PKU is not found and treated soon after birth, symptoms usually start
to appear within a few months after birth. (It takes time for the phenylalanine to build up in the baby's
Early symptoms of
PKU in a baby may include:
- A musty odor to the skin, hair, and
- Skin problems.
- Losing weight from vomiting and
- Acting fussy.
- Being sensitive to
Without early treatment, the child may have
developmental delays, seizures, and severe
How is PKU diagnosed?
babies born in the United States and Canada are tested for PKU within a few days after
birth. This simple blood test may be repeated within the first week or two after birth.
Finding and starting treatment for PKU
early usually can prevent brain damage and other long-term problems.
What treatment do children with PKU need?
The main treatment for PKU is a
lifelong reduced-protein diet. Problems are less likely to occur if your baby starts a PKU diet by age 3 weeks. Your baby’s doctor can help you choose a formula that doesn't contain phenylalanine. You may be able to feed your baby some breast milk, but
talk to your baby’s doctor first. As your child gets older, a
registered dietitian can help you choose the right
foods and recipes.
The medicine sapropterin (Kuvan) may help lower phenylalanine levels in some children with PKU. But more studies are needed to find out the health effects from long-term use. With or without the medicine, your child still needs to follow a PKU diet.