Carrier rate in Sephardic Jews:
Approximately 1 in 35 in North African Jews

Carrier rate in the general population:
Rare

Other ethnic groups in which it occurs:
All other ethnic groups (1 in 100,000 in the general population are affected)

Age of onset of symptoms:
GSD III can begin to manifest in the first few months of life.

Symptoms:
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.

Average lifespan:
With proper management, individuals with GSD III live normal lifespans.

What causes the features of the 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.

Treatment or management:
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.

Carrier testing - number of mutations screened for and detection rate in the Sephardic Jewish population:
Genetic testing of the AGL gene can identify approximately 90% of GSDIII mutations.

Other testing information:
Carrier testing is only performed if there are known mutations in the family. Testing is available to those with a previously affected child or to couples found to be at risk as carriers.

Current research:


For more information:
Association for Glycogen Storage Disease:
   www.agsdus.org
Association for Glycogen Storage Disease UK:
   www.agsd.org.uk
Children Living with Inherited Metabolic Diseases:
   www.climb.org.uk
Madison's Foundation:
   www.madisonsfoundation.org