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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 Overview of Carbohydrate Metabolism Disorders Carbohydrate metabolism disorders are hereditary metabolic disorders. Hereditary disorders occur when parents pass the defective genes that cause these disorders on to their children. There... read more 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 Genes Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells... read more 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.

Glycogen (a carbohydrate Carbohydrates Carbohydrates, proteins, and fats supply 90% of the dry weight of the diet and 100% of its energy. All three provide energy (measured in calories), but the amount of energy in 1 gram (1/28 ounce)... read more ) 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 of Glycogen Storage Diseases

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 Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by drugs taken to control diabetes. Much less common causes of hypoglycemia include other... read more ) 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.

Diagnosis of Glycogen Storage Diseases

  • Blood tests, biopsy, and magnetic resonance imaging

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Treatment of Glycogen Storage Diseases

  • 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.

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