Phenylketonuria (PKU): Condition Information

Phenylketonuria (pronounced fen-l-kee-toh-NOOR-ee-uh), often called PKU, is an inherited disorder that that can cause intellectual and developmental disabilities (IDDs) if not treated. In PKU, the body can't process a portion of a protein called phenylalanine, which is in all foods containing protein. If the phenylalanine level gets too high, the brain can become damaged.

All children born in U.S. hospitals are tested routinely for PKU soon after birth, making it easier to diagnose and treat affected children early.

Children and adults who are treated early and consistently develop normally.1

Depending on the level of phenylalanine and tolerance for phenylalanine in the diet, PKU is classified into two different types: classic, which is the severe form, and moderate. Therefore, each patient needs an individualized treatment plan. Some people may benefit from a medication called sapropterin dihydrochloride (brand name Kuvan®) that treats the disorder.2

Who is at risk for PKU?

Some genetic disorders, including PKU, develop more often among people whose ancestors come from a particular region. People originally from the same region frequently share versions of their genes that have been passed down from common ancestors. These can include genes with mutations or changes that can cause PKU.

In the United States, PKU is most common in people of European or Native American ancestry. It is much less common among people of African, Hispanic, or Asian ancestry.3


  1. NICHD. (2000, updated 2006). Report of the NIH consensus development conference on phenylketonuria (PKU): Screening and management. Retrieved May 15, 2012, from http://www.nichd.nih.gov/publications/pubs/pku/
  2. U.S. Food and Drug Administration. (2007, December). FDA Approves Kuvan for Treatment of Phenylketonuria (PKU), December 13, 2007. Retrieved June 22, 2012, from https://wayback.archive-it.org/7993/20161022203137/http://www.fda.gov/NewsEvents/Newsroom/
    PressAnnouncements/2007/ucm109039.htm
  3. Kaye, C. I., Committee on Genetics, Accurso, F., La Franchi, S., Lane, P. A., Hope, N., et al. (2006). Newborn screening fact sheets. Pediatrics, 118(3), e934–963.