Type I Glycogen Storage Disease

What is type I glycogen storage disease?

Type I glycogen storage disease (GSD I), also known as von Gierke’s disease, is the most common form of glycogen storage disease, accounting for 25% of all cases. It is an inherited disorder that affects the metabolism - the way the body breaks food down into energy.

After we eat, excess glucose is stored in the liver as glycogen to maintain normal glucose levels in our body. In GSD I, the enzyme needed to release glucose from glycogen is missing. When this occurs, a person cannot maintain his or her blood glucose levels and will develop hypoglycemia (low blood sugar) within a few hours after eating. The low levels of glucose in the blood of these individuals often result in chronic hunger, fatigue, and irritability. These symptoms are especially noticeable in infants.

Since people with GSD I are able to store glucose as glycogen but unable to release it normally, stores of glycogen build up in the liver over time and cause it to swell. The liver is able to perform many of its other functions normally, and there is no evidence of liver failure. The kidneys also become enlarged because of increased glycogen storage.

What are the symptoms of type I glycogen storage disease?

Children born with GSD I typically exhibit growth failure, chronic hunger, fatigue, irritability, an enlarged liver, and a swollen abdomen. Blood tests may indicate low blood sugar concentration and higher than normal levels of lipids and uric acid.

What causes type I glycogen storage disease?

GSD I is an inherited genetic disorder which causes the deficiency of one of the enzymes that work together to help the body break down the storage form of sugar (glycogen) into glucose, which the body uses to keep blood sugar stable when a person is not eating.

How is type I glycogen storage disease diagnosed?

Children with GSD I are usually diagnosed between 4 and 10 months of age. Testing will most likely include blood tests, imaging tests such as ultrasound to measure the liver and kidneys, and possibly a genetic test or liver biopsy.

How is type I glycogen storage disease treated?

The treatment of type I glycogen storage disease is focused on correcting the metabolic changes in the body and promoting the growth and development of the child. A combination of uncooked cornstarch mixed in water, soy formula, or soy milk is often recommended. Cornstarch is digested slowly, so it provides a steady release of glucose in between feedings.

Current treatments consist of providing small, frequent feedings during the day. Most doctors agree that certain sugars should be restricted, but the degree of restriction is still debated. In some cases, an overnight tube feeding, typically via a naso-gastric tube, is required to provide a continuous delivery of glucose.

If my child has been diagnosed with type I glycogen storage disease, what should I ask our doctor?

Speak to your doctor about your child’s dietary needs and restrictions.

Who is at risk for type I glycogen storage disease?

GSD I is an inherited genetic disorder. The effects of the disease are apparent very early in childhood.