Overview
Disorder of phenylalanine metabolism is a group of conditions where the body has trouble processing an amino acid called phenylalanine (often shortened to 'Phe'). Amino acids are the building blocks of protein, and phenylalanine is found in many foods we eat. Normally, the body converts phenylalanine into another amino acid called tyrosine using a specific enzyme. When this process does not work properly, phenylalanine can build up in the blood and brain, potentially causing harm to the nervous system. The most well-known condition in this group is phenylketonuria (PKU), but this broader category also includes milder forms sometimes called hyperphenylalaninaemia (HPA) and conditions caused by problems making or recycling the cofactor (called BH4 or tetrahydrobiopterin) that the enzyme needs to work. Symptoms can range from very mild (no noticeable problems) to severe, including intellectual disability, seizures, behavioral issues, and a musty body odor if left untreated. The good news is that newborn screening programs in many countries can detect elevated phenylalanine levels within the first few days of life. Early diagnosis and treatment — usually through a strict low-protein diet and sometimes medication — can prevent most of the serious complications. Treatment options have expanded in recent years, including the FDA-approved medication sapropterin (Kuvan) for BH4-responsive forms and pegvaliase (Palynziq) for adults with PKU. Ongoing management throughout life is important to maintain good health and brain function.
Key symptoms:
Intellectual disability if untreatedSeizuresMusty or mousy body odorLight skin, hair, and eyes compared to family membersEczema or skin rashesBehavioral problems such as hyperactivityAnxiety and depressionDifficulty concentratingTremors or movement problems (especially in BH4 deficiency)Delayed development in untreated infantsIrritabilityMicrocephaly (small head size) if untreatedPoor growth in severe untreated cases
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Neonatal
Begins at or shortly after birth (first 4 weeks)
FDA & Trial Timeline
9 eventsUniversity Hospital, Tours
Central Hospital, Nancy, France
Hospices Civils de Lyon — NA
Gritgen Therapeutics Co., Ltd. — EARLY_PHASE1
University of Missouri-Columbia — NA
Otsuka Pharmaceutical Development & Commercialization, Inc. — PHASE2
Otsuka Pharmaceutical Development & Commercialization, Inc. — PHASE3
BioMarin Pharmaceutical — NA
BioMarin Pharmaceutical — PHASE1, PHASE2
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Disorder of phenylalanine metabolism.
4 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Rare Disease Specialist
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Disorder of phenylalanine metabolism.
Community
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Caregiver Resources
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What specific type of phenylalanine metabolism disorder does my child have, and what gene variants were found?,What is the target phenylalanine blood level we should aim for, and how often should we test?,Is my child a candidate for sapropterin (Kuvan) or other medications?,How do I work with a metabolic dietitian to plan safe and nutritious meals?,What are the long-term risks if phenylalanine levels are not well controlled?,Are there any clinical trials or new treatments we should know about?,What special considerations are needed for pregnancy planning in the future?
Common questions about Disorder of phenylalanine metabolism
What is Disorder of phenylalanine metabolism?
Disorder of phenylalanine metabolism is a group of conditions where the body has trouble processing an amino acid called phenylalanine (often shortened to 'Phe'). Amino acids are the building blocks of protein, and phenylalanine is found in many foods we eat. Normally, the body converts phenylalanine into another amino acid called tyrosine using a specific enzyme. When this process does not work properly, phenylalanine can build up in the blood and brain, potentially causing harm to the nervous system. The most well-known condition in this group is phenylketonuria (PKU), but this broader cate
How is Disorder of phenylalanine metabolism inherited?
Disorder of phenylalanine metabolism follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Disorder of phenylalanine metabolism typically begin?
Typical onset of Disorder of phenylalanine metabolism is neonatal. Age of onset can vary across affected individuals.
Are there clinical trials for Disorder of phenylalanine metabolism?
Yes — 4 recruiting clinical trials are currently listed for Disorder of phenylalanine metabolism on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Disorder of phenylalanine metabolism?
23 specialists and care centers treating Disorder of phenylalanine metabolism are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.