This website is intended for residents of the United States of America interested in Phenylketonuria, also called PKU

With PKU, it’s all about protecting your brain

What is PKU?

PKU is short for phenylketonuria, also known as PAH deficiency, which is a rare genetic condition. In the U.S., about 17,500 people are living with PKU and approximately 350 babies are born with it each year. People affected by PKU have difficulty breaking down phenylalanine (Phe), an amino acid found in all natural protein.

Woman looking at food labels

Food impacts blood Phe levels.

The reason people with PKU can’t break down Phe is that they have a problem with an enzyme called phenylalanine hydroxylase (PAH). PAH breaks down Phe into another amino acid called tyrosine.

Since Phe is found in many foods, such as chicken, meat, eggs, dairy, nuts, grains, and legumes, people with PKU typically eat a special diet.

Learn how you can prevent high blood Phe levels

PKU affects the brain.

The signaling molecules that brain cells use to communicate with each other are called neurotransmitters. When neurotransmitters are not made in the right amounts, the brain cannot function properly. High blood Phe levels can cause disruptions in neurotransmitters like serotonin and dopamine, which are important for mood, learning, memory, and motivation.

In addition to disrupting neurotransmitter balance, Phe itself can be directly toxic to the brain. Scientists think that these changes are behind how high blood Phe affects the way a person thinks, feels, and acts.

Symptoms of high blood Phe levels.

When Phe levels are high or uncontrolled, people with PKU can experience symptoms that have lasting impacts on the brain. Symptoms of high or unstable blood Phe levels include:

  • Feeling “foggy,” or a slowed processing of information
  • Behavioral or social problems
  • Problems with memory
  • Inattention
  • Difficulty in decision making, problem solving, and planning
  • Depression
  • Anxiety
  • Irritability

Use the Symptom Checker to evaluate how PKU may be affecting you

PKU requires lifelong management.

It’s very important to start PKU management early and continue managing PKU for life. In the U.S., newborns are tested for PKU soon after birth as a part of the newborn screening program. PKU experts recommend beginning management as early as possible, starting management within the first week of life. This helps protect an infant’s developing brain from the damaging effects of high or unstable blood Phe levels.

“If I were to go back and talk to my
18-year-old self, I’d say, go back to clinic.”

– Keith, living with PKU for more
than 40 years

It’s never too late to return to care

It wasn’t too long ago that medical experts thought PKU was a condition that was outgrown once the brain was fully developed. However, we now know that high blood Phe levels can be damaging at any stage of development, and that PKU must be managed for life. The brain never fully stops developing. Even those who have not been managing their PKU for many years may see an improvement in some symptoms if they return to management. PKU experts recommend using every available option to control high or unstable blood Phe levels.

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Join the PKU & ME program for support and guidance on living a healthy life with PKU.