Glycogen storage diseases (GSDs) are a group of genetic conditions in which the body being unable to properly store or use glycogen.^1,2 Glycogen is a complex sugar molecule and is a form of stored energy in the body. It is mainly stored in the liver and muscles. When the body needs energy, specialised proteins called enzymes break down glycogen into simpler sugar molecules that are converted into glucose for the body to use. Other specialised proteins called transporters then move the energy to where the body needs it.

GSDs are caused by genetic changes that result in one of these enzymes or transporters being absent or unable to function properly.^1-3 This means the body may not be able to make glycogen, break it down, or move it to where it is needed. As a result, glycogen can accumulate (build-up) in certain parts of the body, or the body may not be able to produce enough glucose when it is needed. The organs most commonly affected are the liver and skeletal muscles, although the heart, kidneys, brain, and other organs may also be involved, depending on the type of GSD.

There are different types of GSD, each caused by a problem with a different enzyme involved in making or breaking down glycogen.¹

Below are some of the different types of GSD; this list may not be complete, and classifications may vary in the literature, particularly as new types continue to be identified and existing conditions get reclassified as new information become available:

• Liver glycogen synthase deficiency (GSD type 0a)  
• Muscle and heart glycogen synthase deficiency (GSD type 0b) 
• Glucose-6-phosphatase deficiency (GSD type Ia)  
• Glucose-6-phosphate transporter deficiency (GSD type Ib)  
• Acid maltase deficiency (Pompe disease) (GSD type II) 
• Glycogen debranching enzyme deficiency (GSD type III)   
• Glycogen branching enzyme deficiency (GSD type IV)   
• Muscle glycogen phosphorylase deficiency (McArdle disease) (GSD type V) 
• Liver glycogen phosphorylase deficiency (Hers disease) (GSD type VI) 
• Phosphofructokinase deficiency (GSD type VII) 
• Phosphorylase kinase deficiency (GSD type IX)  
• Phosphoglycerate mutase deficiency (GSD type X) 
• GLUT2 deficiency (Fanconi–Bickel syndrome)   
• Aldolase A deficiency (GSD type XII)  
• β-enolase deficiency (GSD type XIII)  
• Phosphoglucomutase-1 deficiency (GSD type XIV)  
• Glycogenin-1 deficiency (GSD type XV)  

Synonyms: glycogenosis.²

Universal rare disease classifications provide a common language for recording, reporting and monitoring diseases. Please visit the Rare Disease Classifications page for more information about these internationally recognised classifications.

ORPHA:79201 Glycogen storage disease

ICD-11: 5C51.3 Glycogen storage disease

Please refer to the individual glycogen storage diseases for their specific classifications.

Symptoms can differ depending on the type of GSD a person has, and which parts of the body are affected. Symptoms can also vary between people who have the same type of GSD.^1-3

Common symptoms of GSDs include:

• Low blood sugar (hypoglycaemia)
• Muscle pain, weakness, stiffness or cramps after short periods of exercise
• Enlarged organs (especially the liver), leading to a swollen belly
• Organ dysfunction or, in severe cases, organ failure (often affecting the liver or kidneys)
• Fatigue (tiredness, lack of energy)
• Muscle breakdown (rhabdomyolysis) and, in some types, reduced muscle mass
• Slow weight gain and growth in children
• Cardiomyopathy and arrhythmias in types where glycogen accumulates in the heart

There may be other symptoms specific to a particular type of GSD that has not be listed here. Please speak to your medical team to learn more about the symptoms and complications of a particular type of GSD.

Rare diseases are often serious and progressive, exhibiting a high degree of symptom complexity, leading to significant disability. Majority of the estimated two million Australians living with a rare disease meet the Australian Government’s definition for disability (in accordance to the Australian Public Service Commission and Australian Bureau of Statistics), and many experience severe and permanent disability impacts. If you or someone you care for is experiencing disability-related impacts from a rare condition, please speak with a health or disability professional for advice. Information about relevant disability support can be found at the RARE Portal’s Disability Support Information page.

Glycogen storage diseases (GSDs) are genetic conditions.^1-3 They are caused by disease-causing genetic changes (variants) in genes that control the production or breakdown on glycogen. Each type of glycogen storage disease is caused by variants in a different gene.^1,2

Depending on the GDS type, the condition may be inherited in a different manner. Most GDS are inherited in an autosomal recessive manner, but some may be inherited in a X-linked manner.¹

More information on the relevant inheritance patterns can be found at:

• Centre for Genetics Education: Autosomal recessive inheritance
• Centre for Genetics Education: X-linked inheritance

If you would like to learn more about the inheritance and impact of this condition, please ask your doctor for a referral to a genetic counsellor. Genetic counsellors are qualified allied health professionals who can provide information and support regarding genetic conditions and testing. More information about genetic counselling can be found at:

• Information on Genetic Services
• The National and State Services pages underneath the ‘Genetic Counselling’ sections listed

Diagnosis of GSDs may be based on:^1-3

• clinical examination
• family medical history
• blood tests to measure glucose levels in the blood, including after a period of fasting and in some cases to assess enzyme levels and identify signs of liver, muscle, and other organ involvement, which can help suggest the specific type of GSD.
• imaging tests to assess organ involvemnet
• biopsy (a small sample of tissue) of the muscle or liver in some cases
• genetic testing to confirm diagnosis and determine the type of GSD

As part of the diagnosis process, doctors may rule out other conditions that have similar symptoms (differential diagnosis), muscular dystrophies, spinal muscular atrophy, disorders of glycosylation, fatty acid oxidation disorders, fructose metabolism disorders, organic acidurias, ketogenesis defects, conditions that cause hyperinsulinism, liver disease, and metabolism disorders.^1,3

Please speak to your medical team to learn more about the available pathways for diagnosis of glycogen storage diseases.

There is currently no curative treatment for glycogen storage diseases (GSDs). Treatment is focused on managing symptoms, reducing the risk of complications, and improving quality of life, and may vary depending on the specific type of GSD.¹

Depending on the type of GSD, treatment may involve:^1,3

• Management of muscles through individually tailored physical activity, dietary strategies to increase energy availability before exercise, and learning to recognise and avoid triggers of muscle breakdown or injury. In some cases, severe muscle breakdown (rhabdomyolysis) can occur, which requires urgent medical attention.
• Dietary management with advice from a relevant medical professional – this may include frequent meals, the use of slow-release carbohydrates and careful monitoring of blood sugar levels to prevent episodes of low blood sugar (hypoglycaemia). A metabolic dietitian can help develop an individualised dietary plan.
• Regular monitoring of organs such as the heart, kidney and others
• enzyme replacement therapy (ERT) is available for a small number of glycogen storage diseases and works by replacing the enzyme that is absent or not working in the body – this may help improve symptoms and may slow or stabilise disease progression but is not curative.

Please speak to your medical team to learn more about the possible treatment or management options for your condition. Treatment will depend on an individual’s specific condition and symptoms. It is also important to stay connected to your medical team so that you can be made aware of any upcoming clinical trial opportunities. For many rare diseases, treatment options may be limited. Participation in a clinical trial may provide access to new or emerging therapies.

Healthcare professionals involved in the care of individuals with glycogen storage diseases may include general practitioners (GP), metabolic specialists, dietitians, cardiologists, neurologists, hepatologists (liver specialists), exercise physiologists and genetic counsellors.^{1, 3} The need for different healthcare professionals may change over a person’s lifetime and extend beyond those listed here.

Clinical care for rare diseases often involves a multidisciplinary team of medical, care and support professionals. Please note that the information provided here is as a guide and that RVA does not necessarily monitor or endorse specific clinics or health experts.

This may not be applicable to all rare diseases but for many, palliative care services may be relevant and useful. Palliative care services are available for people (adults, children and their families) living with a life-limiting illness and is not only for end-of-life care. It can also help at any stage of illness from diagnosis onwards, and will look different for different people. Palliative care services provide assistance, support, resources and tools to help people manage their illness and the symptoms, ease pain, and improve comfort and quality of life. If this is relevant to you and you wish to find out more information about palliative care and how it can help you, please visit:

• Australian Institute of Health and Welfare: Palliative care Overview
• Australian Government Department of Health, Disability and Ageing: Palliative care
• Palliative Care Australia

For individuals living with persistent or chronic pain, care pathways may include referral to pain clinics or pain management services. Palliative care services also provide resources, support and tools to help people manage their pain, and may be relevant for some people living with chronic pain. Please speak to your GP about the suitability and possibility of referral to these services.

We are not aware of any clinical care guidelines for glycogen storage diseases as a whole in Australia. If you know of any relevant care guidelines, please let us know via the Contribute page.

International consensus clinical practice guidelines have been developed for several types of GSD, however, there may be information that is not relevant or applicable to the Australian context, and may not be up to date.³

Individuals living with rare diseases may have complex medical issues and disabilities, which are not always visible. It is often useful to refer to their medical history as well as personal information such as a medical card, doctor’s letter, or if available, a rare disease passport, for relevant information.

In addition, individuals, their parents, families and carers often develop extensive expertise on their specific rare disease. It is important to recognise that they can contribute valuable knowledge about their rare condition. Rare diseases often impact individuals differently, so it’s important to consider a person’s lived experience.

It may be important to consider the following when managing individuals living with glycogen storage diseases at emergency departments/services:

• Some individuals with GSDs may have risks specific to their condition (such as hypoglycaemia or rhabdomyolysis)²

There are specific considerations around participating in rare disease research, including clinical trials. It is important to be mindful of issues such as data privacy, research ethics, consent and differences in research regulations between Australia and other countries. For more information, please visit the RARE Portal’s Considerations for Participating in Health and Medical Research page.

If you are interested in finding clinical trials for your condition, please visit the following websites; however, there may not be any clinical trials available:

• Australian Clinical Trials
• ClinicalTrials.gov

It is best to discuss your interest in research, including clinical trials,  with your medical team to determine suitability and eligibility.

Australian Organisation:
We are not aware of any rare disease organisations for GSDs as a whole in Australia. If you are aware of any relevant organisations, please let us know via the Contribute page.

There may be specific support groups for a particular type of GSD.

Genetics Alliance Australia (GAA) may be able to provide some support for families and individuals affected by an undiagnosed or rare genetic condition for which there is no disease specific organisation in Australia.

Please note that RVA does not monitor or endorse each group/organisation’s operational governance and activities. When engaging with a group, please consider the information on the RARE Portal’s Finding Helpful Peer and Community Supports page.

Glycogen storage diseases vary between individuals, and each person’s experience is unique.

If you would like to share your personal story with RVA, please visit the Rare Voices Australia: Share Your Story page. RVA will consider your story for publishing on our website and inclusion on the RARE Portal.

For information on available government and social services that provide support for individuals with a rare disease, please visit the National and State Services pages.

People living with a rare disease often face unique challenges such as diagnostic delays, misdiagnoses, limited treatment options, and limited access to rare disease specialists and support. These challenges may impact people’s emotional wellbeing and quality of life. Many find it helpful to seek mental health and wellbeing support to cope with ongoing stress and uncertainty. Connecting with people who have shared experiences through a support group may also be helpful. Information about relevant mental health and wellbeing support can be found at:

• Mental Health and Wellbeing Support for Australians Living with a Rare Disease
• The National and State Services pages underneath the ‘Mental Health’ sections listed

Further information on glycogen storage diseases can be found at:

• Cleveland Clinic: Glycogen Storage Disease (GSD)
• Johns Hopkins Medicine: Glycogen Storage Disease
• Boston Children’s Hospital: Glycogen Storage Disease

StatPearls: Glycogen Storage Disease

Orphanet: Glycogen storage disease

This page has been developed by Rare Voices Australia (RVA)’s RARE Portal team.

If you are aware of any additional information that may benefit stakeholders with an interest in this page, or if you notice any broken links or inaccurate information, please let us know via the Contribute page.