What is phenylketonuria

Phenylketonuria (PKU) is a rare genetic condition caused by the buildup of the amino acid phenylalanine. Amino acids are the building blocks of protein in the body. Phenylalanine is an “essential” amino acid, meaning it is only obtained through the diet. For an individual to inherit PKU, they must inherit a genetic defect from both parents that carries instructions for making the enzyme (phenylalanine hydroxylase) that breaks down phenylalanine. The enzyme may work less than normal or not at all. In PKU, the excess phenylalanine accumulates in the blood and is toxic to the brain. Infants with PKU may not present with symptoms initially, but without treatment could experience severe intellectual disability, seizures, and additional neurologic problems. The goals of treatment in PKU are to enhance enzyme activity and control dietary intake of phenylalanine with a low-phenylalanine diet to prevent the accumulation of phenylalanine.

How common is phenylketonuria

Phenylketonuria affects approximately 1 in every 10,000 newborns in the United States (about 20,000 individuals)1. As a result of newborn screening in all 50 states, PKU cases can be detected shortly after birth and promptly treated to minimize the risk of complications.1

Questions regarding your Rare Disease therapy

You can reach the Rare Disease team, anytime, day or night, seven days a week.

24-hour Customer Service Center


  • 1Genetics home reference. (2012) NIH/NLM. Phenylketonuria. Accessed 9/18/2023 MedLine Plus


What are the symptoms of phenylketonuria

Signs and symptoms of phenylketonuria include, but are not limited to, the following:

  • Intellectual disability (if un-treated, or not treated consistently)
  • Lighter skin, hair, and eyes than siblings without disease
  • Seizures
  • Hyperactivity
  • Jerking movements of the arms or legs
  • Smaller than normal head size
  • Red skin rash with small pimples
  • Body odor caused by build-up of phenylacetic acid in the urine or sweat
  • Vomiting
  • Irritability



The following specialty medication is available at Accredo, a specialty pharmacy for phenylketonuria.

Medication Manufacturer
Javygtor™ (sapropterin dihydrochloride) Cycle Pharmaceuticals
Kuvan® (sapropterin) BioMarin Pharmaceutical, Inc
Palynziq® (pegvaliase-pqpz) BioMarin Pharmaceutical, Inc
Sapropterin Dihydrochloride  Par Pharmaceutical

Financing Your Care

Financial assistance is available to support your drug costs including manufacturer and community programs. Accredo specialists are available to assist in finding the right program for you.

Financial Guidance

Life-saving specialty medication can be expensive. Learn how the Accredo teams help individuals find ways to afford the medication they need to survive in this video.

Find Support

There are many organizations that support research and advocacy for Phenylketonuria. See below for a few of those organizations.

Support Organizations

Meet the Team

Accredo’s Rare Disease team is dedicated to serving you and we understand the complexity of your condition. Our specialty-trained clinicians are available 24 hours a day, seven days a week, to answer any questions.

Why We Do It

Accredo supports patients with chronic and complex conditions and helps them live their best life. Watch our video to learn why we do what we do for our patients.

Why We Do It video transcript

24-hour Customer Service Center