Overview
2-methylbutyryl-CoA dehydrogenase deficiency (also called 2-methylbutyrylglycinuria or short/branched-chain acyl-CoA dehydrogenase deficiency, sometimes abbreviated as 2-MBD or SBCAD deficiency) is a rare inherited metabolic disorder. It affects the way the body breaks down a building block of protein called isoleucine. Normally, a specific enzyme called 2-methylbutyryl-CoA dehydrogenase helps process isoleucine in the body's cells. When this enzyme does not work properly, a substance called 2-methylbutyrylglycine builds up and is released in the urine. Many people with this condition have no symptoms at all and live healthy lives. However, some individuals — especially children — may experience low muscle tone (floppiness), feeding difficulties, low blood sugar, seizures, or developmental delays. Symptoms can sometimes be triggered by illness, fasting, or times of physical stress. The condition is often picked up through newborn screening programs before any symptoms appear. Treatment mainly focuses on managing diet and avoiding long periods without eating. A metabolic specialist can guide a low-isoleucine diet and recommend supplements if needed. With careful management, most people with this condition do well, though ongoing monitoring is important.
Also known as:
Key symptoms:
Low muscle tone (floppy muscles, especially in infants)Feeding difficulties in newborns or infantsLow blood sugar (hypoglycemia)Seizures or convulsionsDevelopmental delays (slower to reach milestones like sitting or walking)Intellectual disability (in some cases)Fatigue or low energyVomiting, especially during illnessUnusual smell in urinePoor weight gain or failure to thrive in infancy
Clinical phenotype terms (9)— hover any for plain English
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
Treatments
No FDA-approved treatments are currently listed for 2-methylbutyryl-CoA dehydrogenase deficiency.
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Specialists
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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
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Caregiver Resources
NORD Caregiver Resources
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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.Does my child need to follow a special diet, and how strict does it need to be?,What should I do if my child gets sick and cannot eat — do you have a written sick day plan for us?,How often should we have follow-up appointments and what tests will be done?,Are there any signs of a metabolic crisis I should watch for, and when should I go to the emergency room?,Should other family members be tested for this condition?,Will this condition affect my child's development or learning, and what support is available?,Are there any clinical trials or new treatments we should know about?
Common questions about 2-methylbutyryl-CoA dehydrogenase deficiency
What is 2-methylbutyryl-CoA dehydrogenase deficiency?
2-methylbutyryl-CoA dehydrogenase deficiency (also called 2-methylbutyrylglycinuria or short/branched-chain acyl-CoA dehydrogenase deficiency, sometimes abbreviated as 2-MBD or SBCAD deficiency) is a rare inherited metabolic disorder. It affects the way the body breaks down a building block of protein called isoleucine. Normally, a specific enzyme called 2-methylbutyryl-CoA dehydrogenase helps process isoleucine in the body's cells. When this enzyme does not work properly, a substance called 2-methylbutyrylglycine builds up and is released in the urine. Many people with this condition have no
How is 2-methylbutyryl-CoA dehydrogenase deficiency inherited?
2-methylbutyryl-CoA dehydrogenase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.