Disease at a Glance

Summary
Phenylketonuria (PKU) is a genetic metabolic disorder that increases the body's levels of phenylalanine. Phenylalanine is one of the building blocks (amino acids) of proteins. Humans cannot make phenyalanine, but it is a natural part of the foods we eat. However, people do not need all the phenyalanine they eat, so the body converts extra phenylalanine to another harmless amino acid, tyrosine. People with PKU cannot properly break down the extra phenylalanine to convert it to tyrosine. This means phenylalanine builds up in the person's blood, urine, and body. PKU varies from mild to severe. The most severe form is known as classic PKU. Without treatment, children with classic PKU develop permanent intellectual disability. Light skin and hair, seizures, developmental delays, behavioral problems, and psychiatric disorders are also common. Less severe forms, sometimes called "mild PKU", "variant PKU" and "non-PKU hyperphenylalaninemia", have a smaller risk of brain damage. Mothers who have PKU and no longer follow a phenylalanine-restricted diet have an increased risk of having children with an intellectual disability, because their children may be exposed to very high levels of phenylalanine before birth. In most cases, PKU is caused by changes (pathogenic variants, also called genetic changes ) in the PAH gene. Inheritance is autosomal recessive manner. Because PKU can be detected by a simple blood test and is treatable, PKU is part of newborn screening.
Estimated Number of People with this Disease
In the U.S. there may be between

3,000 to 30,000

What Information Does GARD Have For This Disease?

Many rare diseases have limited information. Currently GARD is able to provide the following information for this disease:

*Data may be currently unavailable to GARD at this time.
When do symptoms of this disease begin?
The most common ages for symptoms of a disease to begin is called age of onset. Age of onset can vary for different diseases and may be used by a doctor to determine the diagnosis. For some diseases, symptoms may begin in a single age range or several age ranges. For other diseases, symptoms may begin any time during a person's life.
Prenatal
Before Birth
Newborn
Birth-4 weeks
Infant Selected
1-23 months
Child
2-11 years
Adolescent
12-18 years
Adult
19-65 years
Older Adult
65+ years
The common ages for symptoms to begin in this disease are shown above by the colored icon(s).

Symptoms

These symptoms may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom.
This disease might cause these symptoms:
Cardiovascular System

2 Symptoms

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Cardiovascular System

The cardiovascular system is made up of the heart and blood vessels, including the arteries, veins, and capillaries. Common symptoms of problems in the cardiovascular system include high blood pressure, heart rate or heart rhythm problems, chest pain or discomfort, pain or tingling in the hands or feet, and fatigue. Diseases of the cardiovascular system may be diagnosed and treated by a cardiologist.

Causes

This section is currently in development. 

Inheritance

All individuals inherit two copies of most genes. The number of copies of a gene that need to have a disease-causing variant affects the way a disease is inherited. This disease is inherited in the following pattern(s):

Questions:

Next Steps

Talking with the Medical Team

Good communication between the patient, family, and medical team can lead to an accurate diagnosis. In addition, health care decisions can be made together which improves the patient’s well-being and quality of life.

Describing Symptoms

Describe details about the symptoms. Because there may be many different causes for a single symptom, it is best not to make a conclusion about the diagnosis. The detailed descriptions help the medical provider determine the correct diagnosis.

To help describe a symptom:

  • Use a smartphone or a notebook to record each symptom before the appointment
  • Describe each symptom by answering the following questions:
    • When did the symptom start?
    • How often does it happen?
    • Does anything make it better or worse?
  • Tell the medical team whether any symptoms affect daily activities

Preparing for the First Visit

Working with a medical team to find a diagnosis can be a long process that will require more than one appointment. Make better health decisions by being prepared for the first visit with each member of the medical team.

    Make informed decisions about health care: 
    • Prepare a list of questions and concerns before the appointment
    • List the most important questions first, not all questions may be answered in the first visit
    • Ask questions about symptoms, possible diagnoses, tests, and treatment options
    For future appointments:
    • Discuss what was not addressed at the last visit
    • Discuss changes in the quality of life for the patient, family, and caregivers
    • Discuss health goals and other issues in the patient’s and family’s life that may affect the health care decisions
    Take notes during the appointments to help remember what was discussed.

    Last Updated: Nov. 8, 2021