Glucose is a simple sugar. It is a form of carbohydrate. It is the main source of energy for our bodies. Glycogen is the storage form of glucose in our bodies.
Glycogen storage diseases (GSDs) are a group of inherited genetic disorders. They cause glycogen to be improperly formed or released in the body. This results in a build up of abnormal amounts or types of glycogen in tissues.
The main types of GSDs are categorized by number and name and include:
Glycogen is mainly stored in the liver or muscle tissue. As a result, GSDs usually affect functioning of the liver, the muscles, or both.
GSDs are caused by a genetic enzyme defect. It is inherited from both parents.
Normally, enzymes help convert glucose into glycogen for storage. Other enzymes convert the glycogen back to glucose when energy is needed. This happens during activity like exercise. With GSD, some of these enzymes are defective, deficient, or absent.
The abnormal glycogen build up in the liver and/or muscle tissues.
The main risk factor for GSDs is having a family member with this disease. The risk varies with the type of GSD.
Parents with one child with GSD have a 25% of having another child with GSD. In a few of the GSD types, the risk rises to 50%. In this case only male children are affected.
The most common symptoms of GSDs include:
Signs and symptoms of specific types of GSDs include:
The doctor will ask about symptoms and medical history. A physical exam will be done. Diagnosis of GSDs usually occurs in infancy or childhood. It is often done by the symptoms listed above. Tests may include:
This test may be used for an early diagnosis on some types of GSD. It is often done when there is a family history.
In this technique eggs and sperm are harvested from a couple who have a known risk. The egg is fertilized in the lab. The GSD free embryo is then implanted within the mother’s uterus. This technique allows parents to have additional unaffected children. This process may still pose ethical or religious concerns for some couples.
Treatment will depend on the type of GSD and the symptoms. Your doctor will develop a plan based on your specific symptoms.
These general guidelines apply to people with types I, III, IV, VI, and IX. The goal of treatment is to maintain normal blood glucose levels. This may be done with:
These general guidelines apply to people with types V and VII:
The goal of treatment is to avoid muscle fatigue and/or cramps induced by exercise. This is done by:
There is no way to prevent GSDs. However, early treatment can help control the disease once a person has it. If you have a GSD or a family history of the disorder, you may want to consult a genetic counselor. They can help determine the risk for your children.
Association for Glycogen Storage Disease
Canadian Health Network
Canadian Institute for Health Information
Harrison’s Principles of Internal Medicine . 14th ed. New York, McGraw-Hill; 1998.
Merck Manual of Diagnosis & Therapy . 17th ed. Simon and Schuster; 1999.
5/28/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php : FDA approves new treatment for late-onset Pompe disease. US Food and Drug Administration website. Available at: http://www.fda.gov... . Published May 25, 2010. Accessed May 28, 2010.
Last reviewed September 2012 by Kari Kassir, MD
Last Updated: 09/12/2012