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Phenylketonuria (PKU)

Topic Overview

What is phenylketonuria (PKU)?

Phenylketonuria (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 disease.

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 body.)

Early symptoms of PKU in a baby may include:

  • A musty odor to the skin, hair, and urine.
  • Skin problems.
  • Losing weight from vomiting and diarrhea.
  • Acting fussy.
  • Being sensitive to light.

Without early treatment, the child may have growth problems, developmental delays, seizures, and severe intellectual disability.

How is PKU diagnosed?

Screening is recommended for all newborns within a few days after birth.1 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 who have PKU. 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.

Your child will need regular blood tests. He or she may get tested as often as once a week for the first year and then once or twice a month throughout childhood.

It’s normal to feel a wide range of emotions when your child has an illness like PKU. You may want to join a support group. Your doctor can also help.

What treatment do adults with PKU need?

People who have PKU need to follow a reduced-protein diet throughout their lives. For a few people, treatment with sapropterin (Kuvan) may help when used with a PKU diet. Talk to your doctor about the pros and cons of this medicine.

You’ll need regular blood tests to check your phenylalanine level. Testing once a month is suggested.2 If the level builds up, it can affect your IQ and your ability to learn, think, and understand.

Any woman with PKU who is planning to have a baby needs to be very careful to control her phenylalanine levels. Babies born to mothers who have high levels of phenylalanine are at risk for having a very small head, intellectual disability, growth problems, and heart problems. Having regular blood tests and following the PKU diet before and during pregnancy can help protect the baby.

Frequently Asked Questions

Learning about phenylketonuria (PKU):

Being diagnosed:

Getting treatment:

Other Places To Get Help

Organizations

Children's PKU Network
3790 Via De La Valle
Suite 120
Del Mar, CA  92014
Phone: 1-800-377-6677
(858) 509-0767
Fax: (858) 509-0768
Email: pkunetwork@aol.com
Web Address: www.pkunetwork.org
 

The Children's PKU Network is a nonprofit organization that offers networking services, resources, a hotline, and family support.

Genetics Home Reference, U.S. National Library of Medicine
8600 Rockville Pike
Bethesda, MD  20894
Phone: 1-888-FIND-NLM (1-888-346-3656)
Fax: (301) 402-1384
TDD: 1-800-735-2258
Web Address: www.ghr.nlm.nih.gov
 

The Genetics Home Reference provides information on hundreds of genetic conditions. The website has many tools for learning about human genetics and the way genetic changes can cause disease. It also has links to additional resources for people who have genetic conditions and for their families.

March of Dimes
1275 Mamaroneck Avenue
White Plains, NY  10605
Phone: (914) 997-4488
Web Address: www.marchofdimes.com
 

The March of Dimes tries to improve the health of babies by preventing birth defects, premature birth, and early death. March of Dimes supports research, community services, education, and advocacy to save babies' lives. The organization's website has information on premature birth, birth defects, birth defects testing, pregnancy, and prenatal care.

National Institute of Child Health and Human Development
P.O. Box 3006
Rockville, MD  20847
Phone: 1-800-370-2943
Fax: 1-866-760-5947 toll-free
TDD: 1-888-320-6942
Email: NICHDInformationResourceCenter@mail.nih.gov
Web Address: www.nichd.nih.gov
 

The National Institute of Child Health and Human Development (NICHD) is part of the U.S. National Institutes of Health. The NICHD conducts and supports research related to the health of children, adults, and families. NICHD has information on its Web site about many health topics. And you can send specific requests to information specialists.

National PKU News
6869 Woodlawn Avenue NE
Suite 116
Seattle, WA  98115
Email: schuett@pkunews.org
Web Address: www.pkunews.org
 

This organization creates a newsletter and develops other materials (such as diet information and recipes) for people with phenylketonuria (PKU) and for their families. The website includes treatment and support group information, an email discussion group, and links to related websites.

References

Citations

  1. U.S. Preventive Services Task Force (2008). Screening for phenylketonuria (PKU). Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspsspku.htm.
  2. National Institutes of Health (2000). Phenylketonuria (PKU): Screening and management. NIH Consensus Statement, 17(3): 1–33.

Other Works Consulted

  • Aminoff M (2009). Metabolic disorders section of Neurologic disorders. In RK Creasy et al., eds., Creasy and Resnik's Maternal-Fetal Medicine, 6th ed., pp. 1101–1102. Philadelphia: Saunders Elsevier.
  • Durkin MS, et al. (2008). Childhood cognitive disability. In RB Wallace et al., eds., Wallace/Maxcy-Rosenau-Last Public Health and Preventive Medicine, 15th ed., pp. 1173–1183. New York: McGraw-Hill.
  • Feillet F, et al. (2010). Challenges and pitfalls in the management of phenylketonuria. Pediatrics, 126(2): 333–341.
  • Poustie VJ, Wildgoose J (2010). Dietary interventions for phenylketonuria. Cochrane Database of Systematic Reviews (1).
  • Sapropterin (Kuvan) for phenylketonuria (2008). Medical Letter on Drugs and Therapeutics, 50(1287): 43–44.
  • Schwahn BC (2011). Hyperphenylalaninemias. In CD Rudolph et al., eds., Rudolph's Pediatrics, 22nd ed., pp. 561–563. New York: McGraw-Hill.
  • Somaraju UR, Merrin M (2010). Sapropterin dihydrochloride for phenylketonuria. Cochrane Database of Systematic Reviews (6).
  • Thomas JA, Van Hove JLK (2011). Phenylketonuria and the hyperphenylalaninemias section of Inborn errors of metabolism. In WW Hay Jr et al., eds., Current Diagnosis and Treatment: Pediatrics, 20th ed., pp. 1002–1003. New York: McGraw-Hill.

Credits

By Healthwise Staff
Primary Medical Reviewer John Pope, MD - Pediatrics
Specialist Medical Reviewer Chuck Norlin, MD - Pediatrics
Last Revised September 8, 2011

Last Revised: September 8, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Chuck Norlin, MD - Pediatrics

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