Pompe Disease

Inherited glycogen storage disorder

Pompe disease, also known as glycogen storage disease type II (GSD-II) or acid maltase deficiency, is one of 49 known lysosomal storage disorders. Pompe disease is caused by a deficiency or complete lack of an enzyme called acid alpha-1,4-glucosidase (also called acid maltase). If this enzyme doesn't work properly, glycogen builds up in the body's cells and causes damage, mainly to muscles. This can be life-threatening when the breathing and heart muscles are affected.

The name Pompe disease comes from the Dutch pathologist J.C. Pompe, who first described an infant with the disease in 1932.

Pompe disease affects an estimated 5,000 to 10,000 people worldwide. In the United States, it is estimated to affect 1 per 40,000 people.

Symptoms

There are two forms of Pompe disease. Both have the common symptom of muscle weakness. The disease progresses differently depending on how early it begins:

• Infantile form - usually appears within the first few months of life. Infants are weak and have trouble holding up their heads. Their heart muscles become diseased and their hearts become enlarged and weak. The disease progresses rapidly, and children usually die of heart failure and respiratory weakness before their first birthday.
• Late-onset form - symptoms of muscle weakness begin any time from early childhood through adulthood. The disease progresses more slowly than the infantile form, but individuals still have a shortened life expectancy. Symptoms such as difficulty walking or climbing stairs begin and progress slowly over the years. As the disease progresses, individuals become wheelchair dependent or bedridden, and may require a respirator to breathe.

Diagnosis

A diagnosis of Pompe disease is first suggested by the individual's symptoms. In adults, Pompe disease may be confused with other chronic muscle diseases such as multiple sclerosis. Confirmation of the diagnosis can be made by examining the activity of acid alpha glucosidase in cultured skin cells. In adults, a blood test can be used. In Pompe disease, there will be reduced or absent activity of this enzyme.

Treatment

An individual with Pompe disease will need specialized medical care from geneticists, metabolic specialists, and neurologists. Many individuals find a high-protein diet to be helpful, along with an intensive daily exercise program. Frequent medical evaluations are necessary as the disease progresses.

In 2006, the European Medicines Agency (EMEA) and the U.S. Food and Drug Administration (FDA) both granted marketing approval for the drug Myozyme (alglucosidase alfa) for treatment of Pompe disease. Myozyme replaces the enzyme missing in the disease.

_Sources:

"Overview of Pompe Disease." Pompe Community. 2005. Genzyme Corporation. 29 Nov 2007.

"AMD - Acid Maltase Deficiency - Pompe's Disease." 1997. Acid Maltase Deficiency Association. 29 Nov 2007.