Glycogen Storage Diseases

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 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.

  • Causes

    GSDs are caused by a genetic enzyme defect. It is inherited from one or 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 builds up in the liver and/or muscle tissues.

  • Definition

    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 include:

    • Type 0, Liver glycogen synthase deficiency
    • Type I, Von Gierke disease, defect in glucose-6-phosphatase enzyme, the most common type of GSD accounting for 25% of all cases
    • Type II , Pompe’s disease, acid maltase deficiency
    • Type III, Cori’s disease, debrancher enzyme deficiency
    • Type IV, Andersen’s disease, brancher enzyme deficiency
    • Type V, McArdle’s disease, muscle phosphorylase deficiency
    • Type VI, Hers’ disease, liver phosphorylase deficiency
    • Type VII, Tarui’s disease, muscle phosphofructokinase deficiency
    • Type IX, phosphorylase kinase deficiency

    Glycogen is mainly stored in the liver or muscle tissue. As a result, GSDs usually affect functioning of the liver, the muscles, or both.

  • Diagnosis

    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:

    • Biopsy
      of the affected organs
    • Blood and urine samples
    • MRI scan
      to see internal body structures
    • Genetic testing

    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.

  • Prevention

    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.

  • Risk Factors

    The main risk factor for GSDs is having a family member with this disease.

    The risk varies with the type of GSD.

  • Symptoms

    Each type of GSD has specific symptoms.

  • Treatment

    Treatment will depend on the type of GSD and the symptoms. Your doctor will develop a plan based on your specific symptoms.