Overview
Glycogen storage disease due to liver glycogen phosphorylase deficiency, also known as Glycogen Storage Disease type VI (GSD VI) or Hers disease, is a rare inherited metabolic disorder caused by deficiency of the enzyme glycogen phosphorylase in the liver. This enzyme is essential for breaking down glycogen (the stored form of glucose) in the liver to release glucose into the bloodstream, particularly during fasting. When this enzyme is deficient, glycogen accumulates abnormally in the liver, leading to hepatomegaly (enlarged liver) and difficulties maintaining normal blood sugar levels between meals. The disease primarily affects the liver and metabolic regulation. Key clinical features typically present in early childhood and include hepatomegaly, growth retardation, mild hypoglycemia (low blood sugar) particularly during fasting or illness, hyperlipidemia (elevated blood fats), and mild ketosis. Compared to some other glycogen storage diseases, GSD VI is generally considered one of the milder forms. Many patients experience improvement of symptoms with age, and hepatomegaly often decreases during puberty. However, some individuals may develop liver fibrosis. GSD VI is caused by mutations in the PYGL gene, which encodes the liver isoform of glycogen phosphorylase. There is no specific enzyme replacement therapy currently available. Management focuses on dietary interventions, including frequent meals rich in complex carbohydrates, avoidance of prolonged fasting, and in some cases the use of uncooked cornstarch to maintain blood glucose levels, especially overnight. With appropriate dietary management, the prognosis is generally favorable, and most affected individuals lead relatively normal lives. Regular monitoring of liver function, growth parameters, and metabolic status is recommended.
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
Childhood
Begins in childhood, roughly ages 1 to 12
FDA & Trial Timeline
1 eventNational Institute of Environmental Health Sciences (NIEHS) — NA
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 liver glycogen phosphorylase deficiency.
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Rare Disease Specialist
Rare Disease Specialist
Treatment Centers
8 centersSeoul National University Hospital
📍 Seoul, Seoul
Erasmus Medical Center
📍 Rotterdam
👤 Robert Rissmann, Professor
Stanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 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
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
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Disease timeline:
New recruiting trial: GSD VI and GSD IX Natural History
A new clinical trial is recruiting patients for Glycogen storage disease due to liver glycogen phosphorylase deficiency
New trial: Personalized Environment and Genes Study
Phase NA trial recruiting.
New trial: PULSTA Transcatheter Pulmonary Valve Pre-Approval Study
Phase NA trial recruiting. PULSTA TPV System
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Common questions about Glycogen storage disease due to liver glycogen phosphorylase deficiency
What is Glycogen storage disease due to liver glycogen phosphorylase deficiency?
Glycogen storage disease due to liver glycogen phosphorylase deficiency, also known as Glycogen Storage Disease type VI (GSD VI) or Hers disease, is a rare inherited metabolic disorder caused by deficiency of the enzyme glycogen phosphorylase in the liver. This enzyme is essential for breaking down glycogen (the stored form of glucose) in the liver to release glucose into the bloodstream, particularly during fasting. When this enzyme is deficient, glycogen accumulates abnormally in the liver, leading to hepatomegaly (enlarged liver) and difficulties maintaining normal blood sugar levels betwee
How is Glycogen storage disease due to liver glycogen phosphorylase deficiency inherited?
Glycogen storage disease due to liver glycogen phosphorylase 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 liver glycogen phosphorylase deficiency typically begin?
Typical onset of Glycogen storage disease due to liver glycogen phosphorylase deficiency is childhood. Age of onset can vary across affected individuals.
Which specialists treat Glycogen storage disease due to liver glycogen phosphorylase deficiency?
2 specialists and care centers treating Glycogen storage disease due to liver glycogen phosphorylase deficiency are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.