What is glycogen storage disease?
Glycogen is a carbohydrate that serves as one of the primary fuel reserves for the body’s energy needs. Stores of glycogen power the body during times of fasting and exercise. Glycogen storage disease type III (GSD III) is caused by an enzyme deficiency that prevents liver and/or muscle tissue from completely breaking down the stored glycogen into glucose, which the body metabolizes. This progressive buildup of glycogen can cause muscle wasting and organ failure. In the Sephardi community, GSD III is primarily found among Jews of North African descent.

What are the most common symptoms?
GSD III can begin to manifest in the first few months of life. Periods of fasting, of varying lengths, can trigger hypoglycemia (low blood sugar), which can make a child pallid, irritable, lethargic or shaky, and which can lead to more severe symptoms such as seizures or respiratory distress. One of the first visible indicators of GSD III is a swollen or distended belly, which stems from enlargement of the liver from the buildup of glycogen. This can also lead to jaundice, cirrhosis and liver failure. Children may exhibit growth delay, though they usually reach normal height by adolescence. GSD III is considered a muscular dystrophy. Poor muscle tone may be present early on, and later in life some individuals may experience decreased mobility or heart problems due to progressive weakness in the skeletal and/or cardiac muscle.

Is there treatment available?
At this time there is no effective treatment for GSD III, but the symptoms can be managed to a certain extent through diet. Low blood sugar can be controlled with frequent high-carbohydrate meals, and individuals with muscle weakness, or myopathy, have found some success with high-protein diets.

What is the life expectancy for someone with glycogen storage disease?
With proper management, individuals with GSD III live normal lifespans.

How do I find out if I am a carrier?
Carrier testing is only performed if there are known mutations in the family. Genetic testing of the AGL gene can identify approximately 90% of GSDIII mutations. Visit Screening and Counseling for more information. The Center encourages prospective parents to meet with a genetic counselor and get tested before conception, in order to make the best health care decisions for their families.

How is glycogen storage disease diagnosed?
A physician knowledgeable about the disorder can measure the debrancher enzyme activity levels in leukocytes, a liver biopsy or cultured skin fibroblasts. DNA testing may also be used for diagnostic purposes.

Is prenatal diagnosis available?
Testing is available to those with a previously affected child or to couples found to be at risk as carriers.

How can I find out more about glycogen storage disease?

Association for Glycogen Storage Disease and Association for Glycogen Storage Disease UK
The AGSD and AGSD(UK) aim to enable families of and individuals with glycogen storage disease to communicate, share their successes and concerns, share useful findings, provide support as needed, create an awareness of this condition for the public, stimulate research in the various forms of GSD and communicate results and findings. These organizations also provide newsletters and organize workshops.

Madison’s Foundation
Madison's Foundation is dedicated to improving the quality and quantity of information available to parents of children with rare, life-threatening diseases, and to facilitating effective communication among parents, physicians and medical experts.

Children Living with Inherited Metabolic Diseases
CLIMB is the UK's only dedicated organization to provide information and support on all metabolic diseases to children, adults, families, caretakers and professionals.

International organizations

Association Francophone des Glycogénoses

Selbsthilfegruppe Glykogenose Deutschland e.V.

Associazione Italiana Glicogenosi

Asociación Española de Enfermos de Glucogenosis