Definition:
Pompe Disease/Glycogen Storage Disease II (also known as Acid Maltase Deficiancy) is a rare, neuromuscular genetic disorder resulting from a mutated gene that manufactures the enzyme acid alpha-glucosidase (GAA).  The GAA enzyme is responsible for breaking down glycogen in the lysosome.  In individuals afflicted with Pompe Disease, the GAA enzyme is either absent or present in a very low quantity and glycogen builds in the lysosome, resulting in symptoms associated with this disorder.

Pompe Disease is also known as acid maltase deficiency or acid alpha-glucosidase deficiency.  It is a continuum of the types of glycogen storage diseases that vary in severity and in the age of onset of the first symptoms associated with this disorder.  There are four primary forms of Pompe Disease: The classic infantile form, the non-classic infantile, the juvenile form, and the adult form.  The classic infantile form is the most severe.

Pompe Disease is estimated to occur in about one in 40,000 births worldwide.

Symptoms:
Symptoms of the classical form of Pompe Disease begin within the first few months of life and include a severe loss of muscle tone, progressive muscle weakness, and an enlargement and thickening of the heart.  Symptoms include feeding and respiratory problems as a result of congestive heart failure associated with this disease.

Symptoms of the non-classic infantile form are similar to the classic form, excluding an enlargement of the heart.

Symptoms of the juvenile form commonly begin after age two and are marked by a loss of muscle tone.

Symptoms of the adult form include slow, progressive muscle weakness and/or respiratory difficulties.

Inheritance Pattern:
Pompe Disease/Glycogen Storage Disease II is an autosomal recessive disorder.

Life Expectancy:
Life expectancy for the classic infantile form Pompe Disease/Glycogen Storage Disease II is two years of age or younger, resulting from respiratory or cardiac failure.

Life expectancy for the non-classic infantile form Pompe Disease/Glycogen Storage Disease II is early childhood.

Life expectancy for the juvenile form Pompe Disease/Glycogen Storage Disease II is 30 years of age or younger.

Life expectancy for the adult form Pompe Disease/Glycogen Storage Disease II is 50 years of age or younger.

Diagnosis and Testing:
An enzyme assay using blood or tissue samples measures reduced or absent levels of the GAA enzyme.  Children afflicted with infantile-onset typically have lower than 1% of normal GAA enzyme activity levels.  Individuals afflicted with later-onset have lower than 40% of normal GAA enzyme levels.

Treatment:
Enzyme replacement therapy is available for individuals affected by Pompe Disease.  The FDA-approved Myozyme is a synthiszied form of the human enzyme GAA that replaces the missing enzyme in individuals with Pompe Disease.  It works to break down glycogen that accumulates in the lysosome.  This drug is given intravenously and the affected individal must take it throughout all of his or her life.  Myozyme has shown to prolong the overall survival of affected individuals.  The drug costs approximately $300,000 per year and some insurance companies do not cover the expense.

Patient Groups:
Acid Maltase Deficiency Association
P.O. Box 700248
San Antonio, TX 78270
www.amda-pompe.org
tel: (210) 494-6144
fax: (210) 490-7161
Tiffany House
tianrama@aol.com

National Tay-Sachs & Allied Diseases Association
2001 Beacon Street, Suite 204
Boston, MA 02135
www.ntsad.org
tel: (800) 906-8723
fax: (617) 277-0134
Sue R. Kahn, Executive Director
info@ntsad.org