Overview
3-hydroxyacyl-CoA dehydrogenase deficiency (also called HAD deficiency or M/SCHAD deficiency) is a rare inherited metabolic disorder that affects the body's ability to break down certain fats (fatty acids) for energy. The condition is caused by problems with an enzyme called 3-hydroxyacyl-CoA dehydrogenase, which plays a key role in a process called fatty acid oxidation — the way your body converts fat into usable energy, especially during periods of fasting or illness. When this enzyme does not work properly, the body cannot fully break down medium- and short-chain fatty acids. This leads to a dangerous buildup of partially processed fats and a shortage of energy, particularly for organs like the brain, heart, and liver. One of the most serious consequences is hypoglycemia (very low blood sugar), which can occur when a person goes without food for too long or during illness. Affected individuals, usually infants or young children, may experience episodes of lethargy, vomiting, seizures, and in severe cases, life-threatening metabolic crises. Some patients also develop hyperinsulinism, meaning the pancreas releases too much insulin, which further drives blood sugar dangerously low. Treatment focuses on preventing low blood sugar through frequent feeding, avoiding prolonged fasting, and sometimes using medications to manage hyperinsulinism. With early diagnosis and careful management, many patients can do well, but the condition requires lifelong monitoring and dietary vigilance.
Key symptoms:
Low blood sugar (hypoglycemia)Excessive sleepiness or lethargyVomitingSeizuresPoor feeding in infancyFailure to thrive or poor weight gainMuscle weakness or low muscle toneLiver enlargementEpisodes triggered by fasting or illnessIrritabilityExcessive insulin production (hyperinsulinism)Developmental delays if untreatedLoss of consciousness during metabolic crises
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
FDA & Trial Timeline
2 eventsUltragenyx Pharmaceutical Inc — PHASE3
Ultragenyx Pharmaceutical Inc
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for 3-hydroxyacyl-CoA dehydrogenase deficiency.
2 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →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 3-hydroxyacyl-CoA dehydrogenase deficiency.
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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 long can my child safely go without eating, and does this change as they grow?,What should our emergency plan look like during illness, and when should we go to the hospital?,Does my child have hyperinsulinism, and if so, what treatment is recommended?,Will my child need any dietary supplements such as carnitine?,How often should we have follow-up appointments and blood tests?,Should other family members or future pregnancies be tested?,What should I tell my child's school or daycare about this condition?
Common questions about 3-hydroxyacyl-CoA dehydrogenase deficiency
What is 3-hydroxyacyl-CoA dehydrogenase deficiency?
3-hydroxyacyl-CoA dehydrogenase deficiency (also called HAD deficiency or M/SCHAD deficiency) is a rare inherited metabolic disorder that affects the body's ability to break down certain fats (fatty acids) for energy. The condition is caused by problems with an enzyme called 3-hydroxyacyl-CoA dehydrogenase, which plays a key role in a process called fatty acid oxidation — the way your body converts fat into usable energy, especially during periods of fasting or illness. When this enzyme does not work properly, the body cannot fully break down medium- and short-chain fatty acids. This leads to
How is 3-hydroxyacyl-CoA dehydrogenase deficiency inherited?
3-hydroxyacyl-CoA dehydrogenase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does 3-hydroxyacyl-CoA dehydrogenase deficiency typically begin?
Typical onset of 3-hydroxyacyl-CoA dehydrogenase deficiency is infantile. Age of onset can vary across affected individuals.
Are there clinical trials for 3-hydroxyacyl-CoA dehydrogenase deficiency?
Yes — 2 recruiting clinical trials are currently listed for 3-hydroxyacyl-CoA dehydrogenase deficiency on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat 3-hydroxyacyl-CoA dehydrogenase deficiency?
16 specialists and care centers treating 3-hydroxyacyl-CoA dehydrogenase deficiency are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.