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Glycogen Storage Diseases

By

Matt Demczko

, MD, Sidney Kimmel Medical College of Thomas Jefferson University

Last full review/revision Apr 2020| Content last modified Apr 2020
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Topic Resources

Glycogen storage diseases are carbohydrate metabolism disorders that occur when there is a defect in the enzymes that are involved in the metabolism of glycogen, often resulting in growth abnormalities, weakness, a large liver, low blood sugar, and confusion. Glycogen storage diseases occur when parents pass the defective genes that cause these diseases on to their children.

  • Glycogen storage diseases are caused by the lack of an enzyme needed to change glucose into glycogen and break down glycogen into glucose.

  • Typical symptoms include weakness, sweating, confusion, kidney stones, a large liver, low blood sugar, and stunted growth.

  • The diagnosis is made by doing blood tests, by examining a piece of tissue under a microscope (biopsy), and by doing magnetic resonance imaging.

  • Treatment depends on the type of glycogen storage disease and usually involves regulating the intake of carbohydrates.

There are different types of inherited disorders. In many hereditary metabolic disorders, both parents of the affected child carry a copy of the abnormal gene. Because usually two copies of the abnormal gene are necessary for the disorder to occur, usually neither parent has the disorder. (See also Overview of Hereditary Metabolic Disorders.)

Glycogen (a carbohydrate) is made of many glucose molecules linked together. The sugar glucose is the body’s main source of energy for the muscles (including the heart) and brain. Any glucose that is not used immediately for energy is held in reserve in the liver, muscles, and kidneys in the form of glycogen and is released when needed by the body.

Children who have a glycogen storage disease are missing one of the enzymes that is essential to the process of forming glucose into glycogen or breaking down (metabolizing) glycogen into glucose. About 1 in 25,000 infants has some form of glycogen storage disease.

There are many different glycogen storage diseases (also called glycogenoses). Each is identified by a Roman numeral.

Symptoms

Some of these diseases cause few symptoms. Others are fatal. The specific symptoms, age at which symptoms start, and their severity vary considerably between these diseases. For types II, V, and VII, the main symptom is usually weakness (myopathy). For types I, III, and VI, symptoms are low levels of sugar in the blood (hypoglycemia) and protrusion of the abdomen (because excess or abnormal glycogen may enlarge the liver). Low levels of sugar in the blood cause sweating, confusion, and sometimes seizures and coma. Other consequences for children may include stunted growth, frequent infections, and sores in the mouth and intestines.

Glycogen storage diseases tend to cause uric acid (a waste product) to accumulate in the joints, which can cause gout, and in the kidneys, which can cause kidney stones. In type I glycogen storage disease, kidney failure is common at age 11 to 20 years or later.

Diagnosis

  • Blood tests, biopsy, and magnetic resonance imaging

Glycogen storage disease is diagnosed by examining a piece of muscle or liver tissue under a microscope (biopsy) and by doing magnetic resonance imaging (MRI) to detect glycogen in the tissues. Doctors confirm the diagnosis by analyzing the DNA. Other tests, such as liver, skin, muscle, and blood tests, are done to determine the specific type of glycogen storage disease. Genetic testing, which is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder, is also available. See also diagnosis of hereditary disorders of metabolism.

Table
icon

Some Types of Glycogen Storage Diseases

Name*

Affected Organs, Tissues, or Cells

Symptoms

GSD 0

Liver or muscle

Episodes of low blood sugar levels (hypoglycemia) during fasting if the liver is affected

GSD I (von Gierke disease)

Type Ia

Liver and kidney

Enlarged liver and kidney, slowed growth, very low blood sugar levels, and abnormally high levels of acid, fats, and uric acid in blood

Type Ib

Liver and white blood cells

Same as in von Gierke disease

Low white blood cell count, recurring infections, and inflammatory bowel disease

GSD II (Pompe disease)

All organs

Enlarged liver and heart and muscle weakness

GSD III (Cori disease, Forbes disease)

Liver, muscle, and heart

Enlarged liver or cirrhosis, low blood sugar levels, muscle damage, heart damage, and weak bones in some people

GSD IV (Andersen disease)

Liver, muscle, and most tissues

Cirrhosis, muscle damage, and delayed growth and development

GSD V (McArdle disease)

Muscle

Muscle cramps or weakness during physical activity

GSD VI (Hers disease)

Liver

Enlarged liver

Episodes of low blood sugar during fasting

Often no symptoms

GSD VII (Tarui disease)

Skeletal muscle and red blood cells

Muscle cramps during physical activity and red blood cell destruction (hemolysis)

GSD VIII/IX

Liver

Kidneys

Enlarged liver

Low blood sugar

Kidney problems

Short stature

Rickets, weak bones

* There are many different glycogen storage diseases. Each is identified by a Roman numeral.

GSD = glycogen storage disease.

Treatment

  • Carbohydrate-rich diet

  • Prevention of low blood sugar through frequent or nearly continuous feedings

  • Treatments for specific complications

Treatment depends on the type of glycogen storage disease.

For most types, eating many small carbohydrate-rich meals every day helps prevent blood sugar levels from dropping.

For people who have glycogen storage diseases that cause low blood sugar levels, levels are maintained by giving uncooked cornstarch every 4 to 6 hours around the clock, including overnight.

For others, it is sometimes necessary to give carbohydrate solutions through a stomach tube all night to prevent low blood sugar levels from occurring at night.

People who have a glycogen storage disease that affects the muscles should avoid excessive exercise.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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