Glycogen storage disease type 3

What causes glycogen storage disease type 3?

Glycogen storage disease type 3 (GSDIII) is caused by changes (mutations) in the AGL gene. This gene provides instructions for making the glycogen debranching enzyme, which is involved in the breakdown of glycogen - an important source of stored energy in the body. Most mutations in the AGL gene lead to production of a non-working form of the glycogen debranching enzyme; these mutations are usually responsible for causing GSD types IIIa and IIIb. The mutations in the AGL gene that cause types IIIc and IIId presumably lead to the production of glycogen debranching enzyme with reduced function. All AGL mutations, however, lead to the increased buildup of abnormal, partially broken down glycogen within cells. This buildup damages tissues and organs in the body, thereby causing the signs and symptoms of GSDIII.

Last updated on 05-01-20

How is glycogen storage disease type 3 diagnosed?

Glycogen storage disease type 3 (GSDIII) should be suspected when three main features are present: hepatomegaly (enlarged liver), ketotic hypoglycemia (low blood sugar accompanied by ketosis), and elevated serum concentration of transaminases (a type of enzyme) and CK. Debranching enzyme activity (which is deficient in individuals with the condition) can be measured in a liver biopsy, but this is now not typically necessary for diagnosis. Genetic testing of the AGL gene, the only gene known to be associated with GSDIII, confirms the diagnosis.

Last updated on 05-01-20

How is glycogen storage disease type 3 inherited?

Glycogen storage disease type 3 (GSDIII) is inherited in an autosomal recessive manner. This means that mutations in both copies of the disease-causing gene (usually one inherited from each parent) are necessary to cause the condition. Individuals with one abnormal copy of the gene are referred to as carriers; carriers are unaffected and typically do not show any signs or symptoms of the condition. When two carriers for an autosomal recessive condition have children together, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of his/her parents, and a 25% chance to not be a carrier and not have the condition.

Last updated on 05-01-20

How might glycogen storage disease type 3 be treated?

There is not currently a cure for for glycogen storage disease type 3 (GSDIII). In some cases, diet therapy is helpful. Strict adherence to a dietary regimen may reduce liver size, prevent hypoglycemia (low blood sugar), help to reduce symptoms, and allow for growth and development. Management typically includes a high-protein diet with cornstarch supplementation to maintain a normal level of glucose in the blood. In infancy, feeding every three to four hours is typically recommended. Toward the end of the first year of life, cornstarch is usually tolerated and can be used to avoid hypoglycemia. A high-protein diet prevents breakdown of muscle protein in times of glucose need and preserves skeletal and cardiac muscles. Skeletal and cardiac myopathies may be improved with high-protein diet and avoiding excessive carbohydrate intake. Liver transplantation may be indicated for patients with hepatic cancers.

Individuals seeking personal treatment advice should speak with their health care provider.

Last updated on 05-01-20

Name: Metabolic Support UK 5 Hilliards Court Sandpiper Way
Chester Business Park
Chester, CH4 9QP, United Kingdom
Phone: 0845 241 2173 Toll Free: 0800 652 3181 Email: https://www.metabolicsupportuk.org/contact-us Url: https://www.metabolicsupportuk.org
Name: Association for Glycogen Storage Disease PO Box 896
Durant, IA, 52747 , United States
Phone: 1-563-514-4022 Email: info@agsdus.org Url: http://www.agsdus.org
Name: Association for Glycogen Storage Disease UK Old Hambledon Racecourse Sheardley Lane
Droxford, Southampton, SO32 3QY
United Kingdom
Phone: 0300 123 2790 (Office hrs, Mon-Thurs) or 0300 123 2799 (Out of hours) Url: http://www.agsd.org.uk/
Name: Children's Fund for Glycogen Storage Disease Research, Inc. 20 Sherwood Lane
Cheshire, CT, 06410, United States
Phone: 203-272-7744 Email: info@curegsd.org Url: http://www.cureGSD.org
Name: International Association for Muscle Glycogen Storage Disease IAMGSD 746 4th Avenue
San Francisco, CA, 94118,
Email: info@iamgsd.org Url: https://www.iamgsd.org/
Name: International Association for Muscle Glycogen Storage Disease IamGSD 746 4th Avenue
San Francisco, CA, 94118, United States
Email: info@iamgsd.org Url: https://www.iamgsd.org/ Contact form: https://www.iamgsd.org/contact-us

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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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