Overview
Hyperinsulinism-hyperammonemia syndrome (HI/HA syndrome) is a rare inherited metabolic disorder that causes two main problems at the same time: too much insulin in the blood and too much ammonia in the blood. Insulin is the hormone that lowers blood sugar, and when there is too much of it, blood sugar can drop dangerously low — a condition called hypoglycemia. Ammonia is a waste product that the body normally clears away, and when it builds up, it can affect the brain. This condition is also sometimes called glutamate dehydrogenase hyperinsulinism or GLUD1 hyperinsulinism. The syndrome is caused by changes (mutations) in a gene called GLUD1, which controls an enzyme involved in processing certain amino acids, especially after eating protein-rich foods. Because of this, meals high in protein can trigger episodes of low blood sugar. These episodes can cause shakiness, sweating, confusion, and in severe cases, seizures or loss of consciousness. With proper treatment and careful dietary management, many people with HI/HA syndrome can live relatively normal lives. However, some children may develop learning difficulties or epilepsy, especially if low blood sugar episodes are not caught and treated quickly. Early diagnosis and ongoing medical care are very important for the best possible outcome.
Also known as:
Key symptoms:
Low blood sugar (hypoglycemia), especially after eating proteinShakiness or tremblingSweating without obvious causeConfusion or difficulty thinking clearlySeizures or convulsionsElevated ammonia levels in the bloodIrritability or unusual fussiness in infantsPale or clammy skinDifficulty concentrating or learning problemsFatigue or low energyFainting or loss of consciousness in severe episodes
Clinical phenotype terms (12)— hover any for plain English
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for Hyperinsulinism-hyperammonemia syndrome.
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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
No travel grants are currently matched to Hyperinsulinism-hyperammonemia syndrome.
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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.How often should we check blood sugar at home, and what levels should prompt us to act?,What is the right dose of diazoxide for my child, and what side effects should I watch for?,How much protein is safe to eat at one meal, and are there specific foods we should avoid?,Does my child need neurological or developmental testing because of the high ammonia levels?,What should we do in an emergency if my child loses consciousness or has a seizure?,Should other family members be tested for this condition?,Are there any clinical trials or new treatments we should know about?
Common questions about Hyperinsulinism-hyperammonemia syndrome
What is Hyperinsulinism-hyperammonemia syndrome?
Hyperinsulinism-hyperammonemia syndrome (HI/HA syndrome) is a rare inherited metabolic disorder that causes two main problems at the same time: too much insulin in the blood and too much ammonia in the blood. Insulin is the hormone that lowers blood sugar, and when there is too much of it, blood sugar can drop dangerously low — a condition called hypoglycemia. Ammonia is a waste product that the body normally clears away, and when it builds up, it can affect the brain. This condition is also sometimes called glutamate dehydrogenase hyperinsulinism or GLUD1 hyperinsulinism. The syndrome is cau
How is Hyperinsulinism-hyperammonemia syndrome inherited?
Hyperinsulinism-hyperammonemia syndrome follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Hyperinsulinism-hyperammonemia syndrome typically begin?
Typical onset of Hyperinsulinism-hyperammonemia syndrome is infantile. Age of onset can vary across affected individuals.
Which specialists treat Hyperinsulinism-hyperammonemia syndrome?
1 specialists and care centers treating Hyperinsulinism-hyperammonemia syndrome are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.