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 I (GSD I) is caused by an enzyme deficiency that prevents the body from completely breaking down the stored glycogen into glucose, which the body metabolizes. This progressive buildup of glycogen can cause impaired growth, bleeding problems and enlarged liver and kidneys. There are two main subtypes of GSD I, caused by mutations in two different genes. GSD Ia is most common subtype in Caucasians, with a relatively high carrier frequency in Ashkenazi Jews.

What are the most common symptoms?
GSD I 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 I is a swollen or distended belly, which stems from enlargement of the liver from the buildup of glycogen. Children with GSD I have poor growth resulting in short stature in adulthood. Bleeding problems and renal disease can also result. Developmental delay can occur as a secondary effect of chronic hypoglycemia.

Is there treatment available?
GSD I is mainly treated by strict dietary management. Low blood sugar can be controlled with frequent high-carbohydrate meals and glucose infusions, thus preventing the major complications of the disorder. Additional treatments are available to address or prevent other complications, such as gout, renal disease, and increased lipid levels.

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

How do I find out if I am a carrier?
Genetic testing for GSD Ia can identify 99% of Ashkenazi Jewish carriers. 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 make the diagnosis based on the clinical presentation and laboratory findings, including abnormal levels of glucose, lactate, uric acid and lipids. 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
The AGSD is a parent and patient oriented support group that is advised by a group of experienced medical professionals. In addition to raising awareness and educating others, the AGSD mails out a newsletter, The Ray, which is published quarterly.

Children Living with Inherited Metabolic Diseases (CLIMB)
CLIMB operates out of the United Kingdom and works to maintain and advance our position as the primary provider of metabolic disease specific information and support to children, young people, adults, families and professionals in the UK, and to provide information and support to families worldwide, to fund educational and primary research programs and to investigate treatments and medical services.

Madisons Foundation
Madisons 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. It is the only website in the world that connects parents whose children have the same rare disease.