Glycogen storage disease type II (also called Pompe disease or acid maltase deficiency) is an autosomal recessive metabolic disorder which damages muscle and nerve cells throughout the body. It is caused by an accumulation of glycogen in the lysosome due to deficiency of the lysosomal acid alpha-glucosidase enzyme. It is the only glycogen storage disease with a defect in lysosomal metabolism, and the first glycogen storage disease to be identified, in 1932.
The build-up of glycogen causes progressive muscle weakness (myopathy) throughout the body and affects various body tissues, particularly in the heart, skeletal muscles, liver and nervous system.
Pompe disease is a rare, inherited and often fatal disorder that disables the heart and muscles. It is caused by mutations in a gene that makes an enzyme called alpha-glucosidase (GAA). Normally, the body uses GAA to break down glycogen, a stored form of sugar used for energy. But in Pompe disease, mutations in the GAA gene reduce or completely eliminate this essential enzyme. Excessive amounts of glycogen accumulate everywhere in the body, but the cells of the heart and skeletal muscles are the most seriously affected. Researchers have identified over 300 different mutations in the GAA gene that cause the symptoms of Pompe disease, which can vary widely in terms of age of onset and severity.
Incidence & Prevalence
Current estimates for Pompe disease put the overall disease incidence at approximately 1 in 40,000 live births.
However, as with any rare disease, it is difficult to know exactly how many people are actually affected. Extrapolating from the assumed incidence figures, it is estimated that the current worldwide prevalence may be 5,000-10,000 people—of both genders and of varying ages and ethnicities.
The estimated incidence of 1 in 40,000 reflects a worldwide average. However, several studies suggest that incidence rates may vary rates among populations, and reported estimates range from 1 in 14,000 to 1 in 300,000, depending on geographic area or ethnic group examined.
In infants, the disease appears to be more common among African-Americans and in southern China and Taiwan, while adults with Pompe disease may have a comparatively high incidence in the Netherlands. In addition, some of the specific GAA gene mutations have been identified as more common within certain groups.
- Ausems MG, Verbiest J, Hermans MP, et al. Frequency of glycogen storage disease type II in The Netherlands: implications for diagnosis and genetic counseling. Eur J Hum Genet 1999 Sep; 7(6): 713-6.
- Martiniuk F, Chen A, Mack A, et al. Carrier frequency for glycogen storage disease type II in New York and estimates of affected individuals born with the disease. Am J Med Genet 1998; 79: 69-72.
- Hirschhorn, Rochelle and Arnold J. J. Reuser. Glycogen Storage Disease Type II: Acid Alpha-Glucosidase (Acid Maltase) Deficiency. In: Scriver C, Beaudet A, Sly W, Valle D, editors. The Metabolic and Molecular Bases of Inherited Disease. 8th Edition. New York: McGraw-Hill; 2001; 3389-3420.