Pompe’s disease is a rare genetic disorder that belongs to a group of diseases known as glycogen storage diseases. Affecting only one in every 40,000 people in the United States, Pompe’s disease is characterized by the inability to break down excess glycogen. Glycogen is the body’s main form of carbohydrate, stored primarily in the cells of the liver and muscles.
Under normal circumstances, either the body converts the glycogen to energy, or a part of the cell known as the lysosome breaks down the excess glycogen. Lysosomes are small organs in the cell that act as vacuum cleaners, ridding the cell of excess molecules and bacteria as well as excess glycogen. In order to properly break down glycogen, a special enzyme in the lysosome, known as acid maltase, is needed. People with Pompe’s disease lack this enzyme, hence the disease’s other name, acid maltase deficiency.
Without the acid maltase enzyme keeping the glycogen levels in check, the amount of stored glycogen continues to grow, causing the cell to become larger and larger. The cell eventually becomes non-functioning and dies. As the accumulation of glycogen progresses, cells in the muscles, especially skeletal and heart muscles, become progressively weaker and eventually fail.
Pompe’s disease is inherited in an autosomal recessive pattern. This means that the defective gene must be passed on by each parent. The disease affects both males and females equally. Ethnically, there are higher incidences among certain Chinese and African-American groups who have higher frequencies of certain gene mutations. There are three forms of Pompe’s disease. Generally, they differ in severity by the age at which they occur:
- Infantile form: This form occurs very early in life, usually between 2 and 6 months. Glycogen accumulates in the heart, muscles, liver, and even the neurons (nerve cells) in the spinal cord and brain. It is characterized by severe muscle weakness, hypotonia ("floppiness"), an enlarged heart, a swollen tongue, swallowing problems and respiratory difficulties. This form is usually fatal during the first year of life, generally as a result of cardiopulmonary failure.
- Juvenile form: The juvenile form of Pompe’s disease generally begins to show in the second year of life, often delaying when a child walks. While the heart and liver are usually unaffected by this form, muscle weakness, especially in the shoulders and pelvis, is progressive. Breathing can be critically affected and is often the cause of death. Other symptoms of this form include toe-walking, a waddling gait, enlargement of the calves, and an excessive forward curvature of the back. Life expectancy with this form is usually into the 20s.
- Adult form: The symptoms of this form of Pompe’s disease usually begin between the ages of 30 and 40. Enlargement of organs such as the heart and liver are usually not seen in this form, but muscle weakness, especially in the respiratory muscles, is standard. The muscle weakness generally progresses slowly and is often associated with sleep apnea. Other symptoms include an intolerance to exercise, drowsiness, and a condition known as orthopnea, which is the inability to breathe easily unless sitting straight or standing erect. There is often a decreased bulk in the affected muscles as well as diminished reflexes in the tendons. Patients with this form of Pompe’s disease often live long lives, although not as long as the average life expectancy.
Diagnosis
The best method for testing for Pompe’s disease is a muscle biopsy. During this test, a sample of muscle tissue is taken from the patient and sent to the laboratory for testing. For a person with Pompe’s disease, the tissue sample will show greater-than-normal amounts of glycogen in the cells.
Once Pompe’s disease is diagnosed, other tests are given to determine the degree of cardiac involvement. These tests can include an electrocardiogram (EKG) or an electromyography (EMG), which measure the strength of the heart and other muscles, respectively.
Treatment and management
Research to find a cure for Pompe’s disease involves enzyme replacement and gene therapies. However, an effective treatment has yet to be found. Treatment currently involves managing symptoms and maintaining a healthy lifestyle to prevent further complications. It is especially important for older patients to take steps to prevent respiratory infections.
Symptom management often means physical and occupational therapy. Many adults with Pompe’s disease can complete their daily activities and lead productive lives.
For more information on Pompe’s disease, contact the following organizations:
Association for Glycogen Storage Disease (AGSD)
PO Box 896
Durant, IA 52747-9769
(563) 785-6038
www.agsdus.org
Acid Maltase Deficiency Association (AMDA)
PO Box 700248
San Antonio, Texas 78270-0248
(210) 494-6144
www.amda-pompe.org
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 9/8/2005
