Overview
L-Arginine:glycine amidinotransferase deficiency, also known as AGAT deficiency or guanidinoacetate methyltransferase-related creatine deficiency (though AGAT is the specific enzyme involved), is a rare inherited metabolic disorder. It belongs to a group of conditions called cerebral creatine deficiency syndromes. The body needs creatine to power muscles and the brain. In AGAT deficiency, a faulty gene causes the enzyme AGAT to work poorly or not at all. This enzyme is the first step in making creatine naturally in the body. Without enough creatine, the brain and muscles do not get the energy they need to work properly. The most noticeable effects are on brain development. Children with this condition often have intellectual disability, delayed speech and language, and low muscle tone (called hypotonia). Some children also have autistic-like behaviors or seizures. Because the brain is still developing in early childhood, getting diagnosed and treated early is very important. The good news is that AGAT deficiency is one of the few intellectual disability disorders that can be treated. Giving creatine supplements by mouth can restore creatine levels in the body. When treatment starts early — ideally in infancy — many children show significant improvement in development. Children diagnosed and treated later may still benefit, but early treatment gives the best outcomes. Ongoing monitoring by a metabolic specialist is important for long-term care.
Also known as:
Key symptoms:
Intellectual disability (difficulty with learning and thinking)Delayed speech and language developmentLow muscle tone (floppy muscles, called hypotonia)Delayed motor milestones such as sitting and walkingAutistic-like behaviors (difficulty with social interaction, repetitive behaviors)Seizures or epilepsyBehavioral problemsPoor muscle bulk or weaknessFatigue or low energyDifficulty with daily tasks requiring coordination
Clinical phenotype terms (17)— hover any for plain English
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 L-Arginine:glycine amidinotransferase deficiency.
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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 L-Arginine:glycine amidinotransferase deficiency.
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Caregiver Resources
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Questions for your doctor
Bring these to your next appointment
- Q1.How much creatine supplement does my child need, and how should it be given each day?,Should my child also follow a low-arginine diet, and do we need a dietitian?,How will we know if the treatment is working — what tests or milestones should we track?,What therapies (speech, occupational, physical) should my child start, and how often?,Are there any risks or side effects from long-term creatine supplementation?,Should other family members be tested to see if they are carriers?,Are there any clinical trials or research studies we should know about?
Common questions about L-Arginine:glycine amidinotransferase deficiency
What is L-Arginine:glycine amidinotransferase deficiency?
L-Arginine:glycine amidinotransferase deficiency, also known as AGAT deficiency or guanidinoacetate methyltransferase-related creatine deficiency (though AGAT is the specific enzyme involved), is a rare inherited metabolic disorder. It belongs to a group of conditions called cerebral creatine deficiency syndromes. The body needs creatine to power muscles and the brain. In AGAT deficiency, a faulty gene causes the enzyme AGAT to work poorly or not at all. This enzyme is the first step in making creatine naturally in the body. Without enough creatine, the brain and muscles do not get the energy
How is L-Arginine:glycine amidinotransferase deficiency inherited?
L-Arginine:glycine amidinotransferase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does L-Arginine:glycine amidinotransferase deficiency typically begin?
Typical onset of L-Arginine:glycine amidinotransferase deficiency is infantile. Age of onset can vary across affected individuals.
Which specialists treat L-Arginine:glycine amidinotransferase deficiency?
15 specialists and care centers treating L-Arginine:glycine amidinotransferase deficiency are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.