Overview
Disorders of branched-chain amino acid (BCAA) metabolism are a group of rare inherited conditions that affect how the body breaks down three specific building blocks of protein: leucine, isoleucine, and valine. These amino acids are called 'branched-chain' because of their chemical shape. Normally, the body uses special enzymes to process these amino acids for energy. When one of these enzymes is missing or not working properly, the amino acids and their toxic byproducts build up in the blood, urine, and tissues, causing serious harm — especially to the brain and nervous system. The most well-known condition in this group is Maple Syrup Urine Disease (MSUD), named after the distinctive sweet smell of affected babies' urine. Other conditions in this group include isovaleric acidemia, propionic acidemia, methylmalonic acidemia, and related disorders. Symptoms can range from mild to life-threatening and often appear in the newborn period or early infancy, though some milder forms appear later in childhood or adulthood. Common symptoms include poor feeding, vomiting, extreme tiredness, developmental delays, intellectual disability, and metabolic crises that can be dangerous if not treated quickly. Treatment usually involves a carefully controlled low-protein diet, special medical formulas that provide safe nutrition without the harmful amino acids, and sometimes vitamin supplements or medications. Early diagnosis — often through newborn screening — and consistent treatment can greatly improve outcomes and quality of life.
Key symptoms:
Poor feeding or refusal to eat in newbornsVomiting that keeps coming backExtreme tiredness or low energy (lethargy)Unusual sweet or 'maple syrup' smell in urine or earwaxMuscle stiffness or unusual muscle toneSeizuresDevelopmental delays — sitting, walking, or talking later than expectedIntellectual disabilityBehavioral problems or learning difficultiesEpisodes of metabolic crisis (sudden severe worsening, often triggered by illness or fasting)Failure to thrive or poor weight gainBreathing problems in severe casesSkin rash (in some subtypes like isovaleric acidemia)Unusual body odor (sweaty feet smell in isovaleric acidemia)
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
10 eventsTongji Hospital
Sequitur Health Corp. — NA
University Hospital, Martin — NA
The People's Hospital of Gaozhou — NA
Buddhist Tzu Chi General Hospital — NA
Post Graduate Institute of Medical Education and Research, Chandigarh — PHASE4
Oregon Health and Science University — NA
University Hospital, Grenoble — NA
CAMP4 Therapeutics Corporation — PHASE1
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Disorder of branched-chain amino acid metabolism.
6 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 branched-chain amino acid metabolism.
Community
No community posts yet. Be the first to share your experience with Disorder of branched-chain amino acid metabolism.
Start the conversation →Latest news about Disorder of branched-chain amino acid metabolism
Disease timeline:
New recruiting trial: An Observational Study of Carbaglu® for the Treatment of MMA and PA in Adults and Pediatrics
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: Clinical and Laboratory Study of Methylmalonic Acidemia
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: Clinical Study of the Use of Amino Acid Peritoneal Dialysate in Diabetic Patients
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: A Clinical Study of Glycerol Phenylbutyrate in Chinese Patients With Urea Cycle Disorders
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: Study of CMP-CPS-001 in Healthy Volunteers
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: Safety and Efficacy of a Single Suprachoroidal Injection of JWK010 Gene Therapy in Subjects With Oculocutaneous Albinism Type 1 (OCA1)
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: BCAA vs. Rifaximin in Patients With Cirrhosis for Secondary Prophylaxis of HE
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: The Effects of Glucagon on Hepatic Metabolism in People With Type 2 Diabetes After Caloric Restriction
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: Evaluation of Amino Acid Metabolism Changes in Ovarian Cancer
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
New recruiting trial: Understanding the Long-Term Management of Organic Acidemia Patients With CARBAGLU®: A Mixed Methods Approach
A new clinical trial is recruiting patients for Disorder of branched-chain amino acid metabolism
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.Which specific disorder within the branched-chain amino acid group does my child have, and how does that affect treatment?,What is our emergency sick-day plan, and when exactly should we go to the emergency room?,How often do we need blood and urine tests to monitor amino acid levels?,Are there any vitamin supplements or medications that might help in our specific case?,Is liver transplantation something we should consider, and what are the risks and benefits?,What developmental or educational support should we put in place, and how do we access it?,Are there clinical trials or new treatments we should know about?
Common questions about Disorder of branched-chain amino acid metabolism
What is Disorder of branched-chain amino acid metabolism?
Disorders of branched-chain amino acid (BCAA) metabolism are a group of rare inherited conditions that affect how the body breaks down three specific building blocks of protein: leucine, isoleucine, and valine. These amino acids are called 'branched-chain' because of their chemical shape. Normally, the body uses special enzymes to process these amino acids for energy. When one of these enzymes is missing or not working properly, the amino acids and their toxic byproducts build up in the blood, urine, and tissues, causing serious harm — especially to the brain and nervous system. The most well
How is Disorder of branched-chain amino acid metabolism inherited?
Disorder of branched-chain amino acid metabolism follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Are there clinical trials for Disorder of branched-chain amino acid metabolism?
Yes — 6 recruiting clinical trials are currently listed for Disorder of branched-chain amino acid 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 branched-chain amino acid metabolism?
20 specialists and care centers treating Disorder of branched-chain amino acid metabolism are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.