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Glycogen Storage Diseases

By

Matt Demczko

, MD, Mitochondrial Medicine, Children's Hospital of Philadelphia

Medically Reviewed Dec 2021 | Modified Sep 2022
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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 are the main types of macronutrients in food (nutrients that are required daily in large quantities). They supply 90% of the dry weight of the diet and 100%... 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 forming glucose into glycogen

  • Missing one of the enzymes that is essential to 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 medications taken to control diabetes. Much less common causes of hypoglycemia include... 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

Glycogen storage disease is diagnosed by examining a piece of muscle or liver tissue under a microscope (biopsy) and by doing magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more Magnetic Resonance Imaging (MRI) (MRI) to detect glycogen in the tissues. Doctors confirm the diagnosis by analyzing the DNA. Glycogen storage disease type II (Pompe disease) is now part of the screening test for newborns Newborn Screening Tests Many serious disorders that are not apparent at birth can nonetheless be detected by various screening tests. Early diagnosis and prompt treatment can reduce or prevent many disorders that may... read more in many states. Other tests, such as liver, skin, muscle, and blood tests, are done to determine the specific type of glycogen storage disease. Genetic testing Genetic Screening Before Pregnancy Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more 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 Diagnosis Hereditary metabolic disorders are inherited genetic conditions that cause metabolism problems. Heredity is the passing of genes from one generation to the next. Children inherit their parents'... read more .

Table

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.

More Information

The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

NOTE: This is the Consumer Version. DOCTORS: VIEW PROFESSIONAL VERSION
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