Glycogen storage disease type 2

What causes glycogen storage disease type 2?

Mutations in the GAA gene cause glycogen storage disease type 2. The GAA gene provides instructions for producing an enzyme called acid alpha-glucosidase (commonly called acid maltase). This enzyme is active in lysosomes, which are structures that serve as the cell's recycling center. The enzyme normally breaks down glycogen into a simpler sugar called glucose, which is the main energy source for most cells. Mutations in the GAA gene prevent acid alpha-glucosidase from breaking down glycogen, allowing it to build up in the body's cells. Over time, this buildup damages cells throughout the body, particularly muscle cells.

Last updated on 05-01-20

Is glycogen storage disease type 2 inherited?

Glycogen storage disease type 2 is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Last updated on 05-01-20

What is glycogen storage disease type 2?

Glycogen storage disease type 2 , also known as Pompe disease or acid maltase deficiency disease, is an inherited metabolic disorder. While glycogen storage disease type 2 is a single disease, it may be classified in 2 forms according to the rates of disease progression, its severity and the age at which symptoms start. The classic infantile-onset starts before 12 month of age and involves the heart muscle (myocardiopathy). The later-onset form may start before 12 months of age (non-classic infantile- onset), or after 12 months of age, but does not affect the heart. Muscle weakness is a main symptom in all forms. The infantile-onset is the most severe form and, if untreated, it may lead to death from heart failure in the first year of life. The late-onset form is usually milder, but if untreated may lead to severe breathing problems.

Glycogen storage disease type 2 is caused by variants (mutations) in the GAA gene which have instructions to produce the enzyme acid alpha-glucosidase (acid maltase), needed to break down glycogen, a substance that is a source of energy for the body. The enzyme deficiency results in the accumulation of glycogen inside lysosomes, structures within cells that break down waste products within the cell. Accumulation of glycogen in certain tissues, especially muscles, impairs their function.

In 2006, the U.S. Food and Drug Administration (FDA) approved the enzyme replacement therapy Myozyme as a treatment for all patients with glycogen storage disease type 2. Another similar drug called Lumizyme has recently been approved for the treatment this disease. Additional treatment of Pompe disease is symptomatic and supportive and may include respiratory and feeding support and physical therapy.

Last updated on 05-01-20

How might glycogen storage disease type 2 be treated?

Individuals with glycogen storage disease type 2 are best treated by a team of specialists (such as cardiologist, neurologist, and respiratory therapist) knowledgeable about the disease, who can offer supportive and symptomatic care. The discovery of the GAA gene has led to rapid progress in understanding the biological mechanisms and properties of the GAA enzyme. As a result, an enzyme replacement therapy has been developed that has shown, in clinical trials with infantile-onset patients, to decrease heart size, maintain normal heart function, improve muscle function, tone, and strength, and reduce glycogen accumulation. A drug called alglucosidase alfa (Myozyme©) has received FDA approval for the treatment of glycogen storage disease type 2. Myozyme is a form of GAA—the enzyme that is absent or reduced in this condition. The drug is usually administered via intravenous infusion every other week. Myozyme has been remarkably successful in reversing cardiac muscle damage and in improving life expectancy in those with the infantile form of the disease. To find out more information on Myozyme, please visit the following link: http://www.myozyme.com/. Another alglucosidase alfa drug called Lumizyme has also been approved for the treatment of this condition. More information about Lumizyme can be accessed through the following link: http://www.lumizyme.com/patients.aspx.

Last updated on 05-01-20

Management Guidelines

ACMG - Pompe

The American College of Medical Genetics (ACMG) provides education, resources, and a voice for the medical genetics profession. To make genetic services available to and improve the health of the public, the ACMG promotes the development and implementation of methods to diagnose, treat and prevent genetic diseases. In an effort to fulfill its mission, the ACMG performs many tasks, including developing clinical practice guidelines. In May 2006, the ACMG Work Group on Management of Pompe Disease released a ACMG Practice Guideline titled "Pompe disease diagnosis and management guideline." To view this practice guideline, visit the link above.

Last updated on 04-27-20

Patient Registry

Pompe Registry

The Pompe Registry supports research for Glycogen storage disease type 2 by collecting information about patients with this diagnosis. You can join the registry to share your information with researchers and receive updates about participating in new research studies. Learn more about registries.

Last updated on 04-27-20

Press Releases

FDA - Pompe disease

The U.S. Food and Drug Administration (FDA) provides information about an FDA-approved treatment for Pompe disease called Myozyme through a 2006 Press Release. To view this information, click on the above link.

Last updated on 04-27-20

Selected Full-Text Journal Articles

Free full text - Talsma et al. Pompe

Last updated on 04-27-20

Free full text - Van den Hout, et al., Pompe

Last updated on 04-27-20

Name: Metabolic Support UK 5 Hilliards Court Sandpiper Way
Chester Business Park
Chester, CH4 9QP, United Kingdom
Phone: 0845 241 2173 Toll Free: 0800 652 3181 Email: https://www.metabolicsupportuk.org/contact-us Url: https://www.metabolicsupportuk.org
Name: Association for Glycogen Storage Disease PO Box 896
Durant, IA, 52747 , United States
Phone: 1-563-514-4022 Email: info@agsdus.org Url: http://www.agsdus.org
Name: Association for Glycogen Storage Disease UK Old Hambledon Racecourse Sheardley Lane
Droxford, Southampton, SO32 3QY
United Kingdom
Phone: 0300 123 2790 (Office hrs, Mon-Thurs) or 0300 123 2799 (Out of hours) Url: http://www.agsd.org.uk/
Name: Acid Maltase Deficiency Association (AMDA) P.O. Box 700248
San Antonio, TX, 78270, United States
Phone: 210-494-6144 Fax : 210-490-7161 Email: tianrama@aol.com Url: http://www.amda-pompe.org
Name: Muscular Dystrophy Association MDA 222 S Riverside Plaza Suite 1500
Chicago, IL, 60606, United States
Toll Free: 1-833-275-6321 (Helpline) Email: resourcecenter@mdausa.org Url: https://www.mda.org
Name: International Pompe Association Paula Waddell, c/o VSN Luitenant Generaal van Heutszlaan 6
3743 JN Baarn
Netherlands
Phone: +31(35)5480480 Fax : +31(35)5480499 Email: info@worldpompe.org Url: http://www.worldpompe.org/

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