Phenylketonuria (PKU) is an inherited metabolic disorder. It is caused by a genetic mutation on Chromosome 12 and results in a child's inability to produce the enzyme that breaks down the amino acid phenylalanine. Phenylalanine (Phe) is one of the 23 amino acids that make up a protein. A person with PKU can break down the other 22 amino acids found in a protein but their body cannot break down the amino acid phenylalanine.
All foods contain some protein and therefore almost all foods contain some Phenylalanine. Even apples, bananas, green beans, lettuce and other fruits and vegetables contain some protein and therefore some phenylalanine.
Families considering the adoption of a child with PKU should click through the resources that can be found at the bottom of this page.
Proper treatment of an individual with PKU includes eating a very strict low protein diet in order to limit the amount of phenylalanine being ingested into the body. Also, a person with PKU needs to daily drink a medically formulated protein drink (also called a medical food). This medically prescribed protein drink provides a person with PKU all the necessary vitamins, minerals, and protein that a body needs.. Failure to treat a person or child with PKU, especially from birth, leads to high build-up of Phe in the blood stream and leads to neurological problems, mood disorders, cognitive delays and a host of other medical problems.
A medical staff consisting of a physician specialized in metabolic genetics, a dietitian, and often a genetic counselor, and social worker or psychologist work with the family to determine the most appropriate treatment of an individual with PKU. Because every patient's PKU genetic mutation is different, their prescribed treatment must be individualized also. Every patient plan begins with a restrictive diet with extremely low amounts of natural protein. A medical food (formula) specifically high in other essential amino acids but low in Phenylalanine is medically prescribed. Some individuals have a more restrictive diet than others, based on their genetic mutation. Foods consumed are measured and calculated to assure the individual does not consume dangerous amounts of phe each day. Despite what was once believed to be a disorder only affecting children, for several decades research has shown that the PKU diet is to be followed for a lifetime.
Foods that are "off limits" to individuals on PKU treatment include meat, poultry, fish, tofu, soy, eggs, nuts/beans, dairy, cheese, most grains, and any foods vegetarians use to add protein to their diets. Some foods are allowed in strict moderation including potatoes and corn. Most fruits and vegetables are allowed in larger quantities, and can be supplemented with specialty foods such as low protein pasta, low protein rice, low protein bread, low protein cookies, dairy replacements, and meat/soy alternatives. These foods may be obtained through certain companies or made at home using a specially made low protein flour.
In recent years, new medications have liberalized the diet for many PKU patients. But, not every person’s PKU mutation responds to the new medications. For PKU patients that do respond to the medication, most still require the special medical food (formula) and some, but fewer, restrictions on the amount of protein/phenylalanine eaten. Research is underway, and in the future, more effective drugs are anticipated to allow a more liberalized diet for more patients.
The future of individuals with PKU greatly depends on many factors. Specific genetic mutation (and therefore the amount of Phenylalanine a child's body can process), the age of diagnosis, the age treatment began, and the quality of treatment over a lifespan all play a role in each individual's prognosis.
Some children in orphanages or foster homes were detected young and their condition was cared for well from a young age. These children will likely have a prognosis similar to their un-affected peers. Other children may have been diagnosed and treated later, or not treated at all prior to adoption. Some of these children are able to catch up with peers intellectually with intensive therapy, but still others will never catch up with peers and will always struggle with low cognitive function and neurological or mood disorders.