Glycogen Storage Disease Type III (Cori/Forbes Disease)
An inherited deficiency of the glycogen debranching enzyme causing hepatomegaly, hypoglycemia, and progressive muscle or heart involvement.
- Autosomal Recessive
- AGL Gene Deficiency
- Liver and Muscle Involvement
- Most Common In
- Infants and young children
- Inheritance
- Autosomal Recessive
- Key Gene
- AGL
- Primary Management
- Dietary Therapy
Condition Overview
Glycogen Storage Disease Type III (Cori or Forbes disease) results from deficiency of the glycogen debranching enzyme (amylo-1,6-glucosidase), encoded by the AGL gene. Without this enzyme, an abnormal, partially degraded form of glycogen accumulates in the liver and, in most patients, skeletal and cardiac muscle.
GSD III is subdivided into Type IIIa, which affects the liver, skeletal muscle, and heart, and Type IIIb, which is limited to the liver. Hypoglycemia tends to be less severe than in GSD I, but myopathy and cardiomyopathy can develop over time, particularly in Type IIIa.
Types and Subtypes
GSD III is classified by the pattern of organ involvement.
Symptoms and Signs
Symptoms usually appear in infancy or early childhood.
Causes and Risk Factors
GSD III is caused by biallelic mutations in the AGL gene.
Diagnosis and Investigations
Diagnosis relies on metabolic testing, enzyme assay, and genetic confirmation.
Disease Severity Classification
GSD III severity is described by organ involvement and metabolic control rather than formal staging.
Standard Treatment
Management focuses on maintaining glucose stability and supporting muscle and cardiac health.
Advanced & Emerging Therapies
Research is exploring enzyme and gene-based approaches for GSD III.
Gene Therapy
Investigational AGL Gene Replacement
Early-stage research is exploring gene therapy approaches to restore debranching enzyme activity.
Dietary Therapy
High-Protein, Modified Cornstarch Regimens
Refined nutritional protocols are being studied to better protect muscle and cardiac tissue.
Biomarkers & Monitoring Parameters
Several markers help track disease activity in GSD III.
When to Seek a Second Opinion
Specialist input is valuable at several points in GSD III management.
Clinical Trials & Research
Prognosis & Outcomes
Outcomes in GSD III vary depending on the degree of muscle and cardiac involvement.
Supportive Care
A multidisciplinary approach supports quality of life in GSD III.
How CancerFax Helps You Explore Treatment Options
CancerFax helps families affected by GSD Type III access metabolic and cardiology specialists, review genetic test results, and explore current research into gene therapy and dietary management approaches.
Get a free case reviewFrequently Asked Questions
GSD Type III (Cori or Forbes disease) is caused by deficiency of the glycogen debranching enzyme, leading to abnormal glycogen buildup in the liver and, in many patients, skeletal and cardiac muscle.
Type IIIa affects the liver, skeletal muscle, and heart, while Type IIIb is limited to the liver due to a tissue-specific AGL mutation.
It is caused by inherited biallelic mutations in the AGL gene, passed down in an autosomal recessive pattern.
Diagnosis involves fasting metabolic testing, creatine kinase and liver enzyme measurement, echocardiography, and confirmatory AGL gene sequencing.
Treatment includes frequent feeding, uncooked cornstarch therapy, a high-protein diet, and regular cardiac and muscle monitoring.
Type IIIa can be associated with cardiomyopathy, which is why regular echocardiogram monitoring is recommended.
Liver-related symptoms often improve with age, but muscle and cardiac involvement in Type IIIa can progress in adulthood, making lifelong specialist follow-up important.
Yes. CancerFax can review your medical reports and genetic test results, help coordinate second opinions with metabolic disease specialists, and assist in exploring enzyme replacement therapy, gene therapy trials, or transplant evaluation at centers in India, China, and internationally.