National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Mild phenylketonuria


Other Names:
Mild PKU; mPKU; Variant phenylketonuria; Mild PKU; mPKU; Variant phenylketonuria; Variant PKU See More
Categories:
Mild phenylketonuria is a rare form of phenylketouria (PKU variant), an inborn error of amino acid metabolism, characterized by symptoms of PKU of mild to moderate severity. Patients with blood phenylalanine concentrations of 600-1,200 micromol/L are considered to have mild PKU. Clinical signs include reduced cognitive function and behavioral and developmental disorders. It is caused by certain mutations in the PAH gene which result in slightly higher activity of the phenylalanine hydroxylase compared with the classic phenylketonuria where there is a complete or near-complete deficiency of phenylalanine hydroxylase activity. Inheritance is autosomal recessive. Treatment is with a diet low in phenylalanine (patients can have up to 400-600 mg/day of phenylalanine).[1][2]
Last updated: 12/28/2015

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Newborn Screening

  • An ACTion (ACT) sheet is available for this condition that describes the short-term actions a health professional should follow when an infant has a positive newborn screening result. ACT sheets were developed by experts in collaboration with the American College of Medical Genetics.
  • An Algorithm flowchart is available for this condition for determining the final diagnosis in an infant with a positive newborn screening result. Algorithms are developed by experts in collaboration with the American College of Medical Genetics.
  • Baby's First Test is the nation's newborn screening education center for families and providers. This site provides information and resources about screening at the local, state, and national levels and serves as the Clearinghouse for newborn screening information.
  • The Newborn Screening Coding and Terminology Guide has information on the standard codes used for newborn screening tests. Using these standards helps compare data across different laboratories. This resource was created by the National Library of Medicine.
  • National Newborn Screening and Global Resource Center (NNSGRC) provides information and resources in the area of newborn screening and genetics to benefit health professionals, the public health community, consumers and government officials.

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

  • Sapropterin (Brand name: Kuvan) - Manufactured by Biomarin Pharmaceutical Inc.
    FDA-approved indication: December 2014 approved to reduce blood phenylalanine (Phe) levels in patients with hyperphenylalaninemia (HPA) due to tetrahydrobiopterin- (BH4-) responsive Phenylketonuria (PKU). Kuvan is to be used in conjunction with a Phe-restricted diet.
    National Library of Medicine Drug Information Portal
    Medline Plus Health Information
  • Pegvaliase (Brand name: Palynziq) - Manufactured by BioMarin Pharmaceutical
    FDA-approved indication: May 2018 approved to reduce blood phenylalanine concentrations in adult patients with phenylketonuria (PKU) who have uncontrolled blood phenylalanine concentrations greater than 600 micromol/L on existing management.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Patient Registry

  • A registry supports research by collecting of information about patients that share something in common, such as being diagnosed with Mild phenylketonuria. The type of data collected can vary from registry to registry and is based on the goals and purpose of that registry. Some registries collect contact information while others collect more detailed medical information. Learn more about registries.

    Registries for Mild phenylketonuria:
    NBS Connect
    PKU Patient Registry
    The PKU Registry
     

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Parent and Caregiver Resources

  • In this NCATS Video Profile, Jennifer Payne discusses living with phenylketonuria (PKU). Left untreated, PKU results in psychological disorders, neurological deterioration, mental illness and brain damage. Dietary management and access to medical foods are a critical part of PKU care.

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Regier DS, Greene CL. Phenylalanine Hydroxylase Deficiency. GeneReviews. January 5, 2017; http://www.ncbi.nlm.nih.gov/books/NBK1504/.
  2. Mild phenylketonuria. Orphanet. April, 2012; http://www.orpha.net/consor4.01/www/cgi-bin/Disease_Search.php?lng=EN&data_id=11279. Accessed 12/28/2015.