Overview
Glycogen storage disease due to glycogen debranching enzyme deficiency, also known as Glycogen Storage Disease type III (GSD III), Cori disease, or Forbes disease, is a rare inherited metabolic disorder caused by deficiency of the glycogen debranching enzyme (amylo-1,6-glucosidase, 4-alpha-glucanotransferase), encoded by the AGL gene. This enzyme is essential for the complete breakdown of glycogen into glucose. When it is deficient, an abnormal form of glycogen (limit dextrin) accumulates in affected tissues, primarily the liver, skeletal muscle, and heart. The disease typically presents in infancy or early childhood with hepatomegaly (enlarged liver), hypoglycemia (low blood sugar) during fasting, growth retardation, and elevated liver transaminases and serum lipids. GSD III is classified into subtypes: type IIIa (approximately 85% of cases) involves both liver and muscle, while type IIIb affects only the liver. Patients with muscle involvement (type IIIa) may develop progressive myopathy and cardiomyopathy, which can become clinically significant in adulthood. Liver symptoms often improve with age, though some patients may develop liver fibrosis or cirrhosis, and rarely hepatocellular carcinoma. Management is primarily dietary and supportive. Frequent meals rich in complex carbohydrates, high-protein diets, and uncooked cornstarch supplementation are used to prevent hypoglycemia and provide alternative energy substrates for muscle. Overnight continuous glucose feeds or cornstarch may be necessary in young children. Cardiac function and muscle strength should be monitored regularly in patients with type IIIa. There is currently no approved enzyme replacement therapy or gene therapy for GSD III, although research into these approaches is ongoing. A multidisciplinary team including metabolic specialists, cardiologists, hepatologists, and dietitians is recommended for optimal care.
Also known as:
Clinical phenotype terms— 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
FDA & Trial Timeline
3 eventsUniversity Hospital, Strasbourg, France
Smith & Nephew, Inc. — NA
Institut de Myologie, France
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Glycogen storage disease due to glycogen debranching enzyme deficiency.
1 clinical trialare 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
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Disease timeline:
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A new clinical trial is recruiting patients for Glycogen storage disease due to glycogen debranching enzyme deficiency
New recruiting trial: French Observatory for Patients with Type 3 Glycogenosis
A new clinical trial is recruiting patients for Glycogen storage disease due to glycogen debranching enzyme deficiency
New recruiting trial: Non-invasive Assessment of Liver Fibrosis in a French Cohort of Pediatric Patients With Type III Glycogen Storage Disease: Current State and Perspectives
A new clinical trial is recruiting patients for Glycogen storage disease due to glycogen debranching enzyme deficiency
New trial: Pompe Pregnancy Sub-Registry
Phase NA trial recruiting.
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Common questions about Glycogen storage disease due to glycogen debranching enzyme deficiency
What is Glycogen storage disease due to glycogen debranching enzyme deficiency?
Glycogen storage disease due to glycogen debranching enzyme deficiency, also known as Glycogen Storage Disease type III (GSD III), Cori disease, or Forbes disease, is a rare inherited metabolic disorder caused by deficiency of the glycogen debranching enzyme (amylo-1,6-glucosidase, 4-alpha-glucanotransferase), encoded by the AGL gene. This enzyme is essential for the complete breakdown of glycogen into glucose. When it is deficient, an abnormal form of glycogen (limit dextrin) accumulates in affected tissues, primarily the liver, skeletal muscle, and heart. The disease typically presents in i
How is Glycogen storage disease due to glycogen debranching enzyme deficiency inherited?
Glycogen storage disease due to glycogen debranching enzyme deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Glycogen storage disease due to glycogen debranching enzyme deficiency typically begin?
Typical onset of Glycogen storage disease due to glycogen debranching enzyme deficiency is infantile. Age of onset can vary across affected individuals.
Are there clinical trials for Glycogen storage disease due to glycogen debranching enzyme deficiency?
Yes — 1 recruiting clinical trial is currently listed for Glycogen storage disease due to glycogen debranching enzyme deficiency on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Glycogen storage disease due to glycogen debranching enzyme deficiency?
2 specialists and care centers treating Glycogen storage disease due to glycogen debranching enzyme deficiency are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.