Glycogen Storage Disease Type II (Pompe Disease)

Gene : GAA

What is Glycogen Storage Disease Type II?

Glycogen Storage Disease Type II (GSD II), also known as Pompe disease, is an inherited disorder caused by excessive accumulation of glycogen, a type of complex sugar, in cells. This is due to a defective enzyme called acid alpha-glucosidase, also known as acid maltase. Affected organs and tissues may include muscles, heart and liver. Intellect is not affected. Based on the severity and the age at which symptoms appear, GSD II is categorized into two types, infantile-onset or late-onset. The infantile-onset type of GSD II is the most common and usually begins within the first year of life, leading to death from heart failure or breathing problems in early childhood. The late-onset type of GSD II may not become apparent until later in childhood, adolescence, or early adulthood, and has similar but less severe symptoms. Persons with late-onset type of GSD II usually have progressive muscle weakness and breathing problems, and shortened life spans. It is not possible to predict the severity of the condition for any particular person.Enzyme replacement therapy as soon as the diagnosis is established could alleviate symptoms and improve survival. Therapies are also available to manage complications with heart, breathing and muscular problems. GSD II is caused by pathogenic variants in the GAA gene.

How is Glycogen Storage Disease Type II inherited?

GSD II is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant in the gene for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

What does it mean to be a carrier?

There are generally no signs or symptoms associated with being a carrier for GSD II. However, the risk to have a child affected with GSD II is increased. Testing of reproductive partners is recommended for carriers of GSD II.

How common is Glycogen Storage Disease Type II?

GSD II is estimated to affect about 1 in 40,000 newborns in the general American population, but the occurence of GSD II varies among different ethnic groups from 1 in 14,000 newborns in African Americans to 1 in 100,000 newborns in individuals of European descent.

Family References and Resources
Clinician References
What is Analyzed?
  • Full gene sequencing
Affected Systems






Carrier Rates
Detection Rate
Carrier Frequency
African American > 91% 1 in 60
General Population > 91% 1 in 100

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