Overview
Tyrosinemia type 3 (also called HT3 or hydroxyphenylpyruvate dioxygenase deficiency) is a very rare inherited metabolic disorder. It happens when the body cannot properly break down the amino acid tyrosine, which is a building block of protein found in many foods. The problem is caused by a missing or poorly working enzyme called 4-hydroxyphenylpyruvate dioxygenase (HPPD). Without this enzyme working correctly, tyrosine and its byproducts build up to harmful levels in the blood and urine. The most noticeable effects of tyrosinemia type 3 are on the brain and nervous system. Many people with this condition experience intellectual disability, seizures, and problems with coordination and balance. Unlike the other types of tyrosinemia, this form does not usually cause serious liver or kidney damage, which makes it somewhat different in how it affects the body. Treatment mainly focuses on reducing tyrosine levels through a special low-protein diet and a formula that limits the amino acids phenylalanine and tyrosine. There is no specific FDA-approved drug for this exact condition. With careful dietary management, some symptoms may be reduced, but neurological problems can still persist. Because this disease is so rare, research is ongoing and management is largely guided by metabolic specialists.
Also known as:
Key symptoms:
Intellectual disability or learning difficultiesSeizures or epilepsyProblems with balance and coordination (ataxia)Elevated tyrosine levels in the bloodHigh levels of tyrosine byproducts in the urineDevelopmental delaysBehavioral problemsMild movement difficulties
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for Tyrosinemia type 3.
View clinical trials →Clinical Trials
View all trials with filters →No actively recruiting trials found for Tyrosinemia type 3 at this time.
New trials open frequently. Follow this disease to get notified.
Rare Disease Specialist
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 Tyrosinemia type 3.
Community
No community posts yet. Be the first to share your experience with Tyrosinemia type 3.
Start the conversation →Latest news about Tyrosinemia type 3
No recent news articles for Tyrosinemia type 3.
Follow this condition to be notified when news becomes available.
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
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.How often should we check blood tyrosine levels, and what is the target range?,What specific foods and proteins should be avoided or limited in the diet?,Will the dietary treatment improve or prevent further neurological problems?,What seizure medications are recommended, and what should we do in a seizure emergency?,Are there any clinical trials or new treatments we should know about?,What developmental or educational support services do you recommend?,Should other family members be tested for this condition?
Common questions about Tyrosinemia type 3
What is Tyrosinemia type 3?
Tyrosinemia type 3 (also called HT3 or hydroxyphenylpyruvate dioxygenase deficiency) is a very rare inherited metabolic disorder. It happens when the body cannot properly break down the amino acid tyrosine, which is a building block of protein found in many foods. The problem is caused by a missing or poorly working enzyme called 4-hydroxyphenylpyruvate dioxygenase (HPPD). Without this enzyme working correctly, tyrosine and its byproducts build up to harmful levels in the blood and urine. The most noticeable effects of tyrosinemia type 3 are on the brain and nervous system. Many people with t
How is Tyrosinemia type 3 inherited?
Tyrosinemia type 3 follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Tyrosinemia type 3 typically begin?
Typical onset of Tyrosinemia type 3 is infantile. Age of onset can vary across affected individuals.
Which specialists treat Tyrosinemia type 3?
6 specialists and care centers treating Tyrosinemia type 3 are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.