What is PKU?

Phenylketonuria, abbreviated PKU, is an inherited metabolic disorder that leads to mental retardation and other neurological problems if untreated. It occurs in one of every 10,000 – 15,000 births. With this disorder, the body is unable to metabolize an amino acid called phenylalanine (PHE), a component of protein. Therefore, when a person with PKU consumes PHE-containing foods, the PHE builds up in their body. High levels of PHE can cause damage to the central nervous system. If this problem is left untreated, the consequences are progressive mental retardation, neurological deterioration and behavioral disorders.

Since the mid-1960s, the PKU screening test has been included in the "newborn screening" process. Early detection of PKU is important because treatment, which could potentially prevent neurological damage from occurring, can be initiated immediately. However, if PKU is not diagnosed shortly after birth, the chronically high PHE levels will cause mental retardation and a variety of other problems.

In order for an individual to inherit PKU, that person’s mother and father must carry the PKU gene. If they do, they have a 1 in 4 chance of having a child with the condition. Symptoms of PKU may vary with each individual according to the severity of damage, but some of these include: mental retardation, behavioral disorders such as head-banging, self-injurious behavior and aggression, dry scaly skin, unsteady gait, loss of muscle tone, seizures and spasticity.

Treatment for PKU normally includes dietary control such as eating foods low in PHE and consuming a protein substitute called "medical food." Medical foods contain vitamins, minerals and all essential amino acids except phenylalanine. By limiting intakes of PHE through natural sources and assuring adequate intake of the non-offensive amino acids, the levels of PHE in the blood are maintained at lower levels, allowing for normal growth and development.

Access resources including PKU medical food suppliers and specialty low protein manufacturers as well as various PKU-specific Web sites.

Learn more about the PKU Diet for Life project.