Pompe disease

In the United States and other countries, there is an approved treatment for Pompe disease with a drug called alglucosidase alfa (Trade Name: Lumizyme). Lumizyme is an enzyme replacement therapy (ERT) which is a man-made enzyme that is infused into the vein of a person with Pompe disease every two weeks. The man-made enzyme can break down built up glycogen in the muscles. Lumizyme is better at clearing out glycogen storage in the heart muscles compared with the skeletal muscles (muscles which help the body move). It is important to start ERT as soon as possible when someone is diagnosed with Pompe disease, because muscle that is too damaged by glycogen may not be able to be helped. ERT therapy must be given every two weeks for the rest of the person's life. It is very expensive, but health insurance usually most of the cost of the medicine. If you want to consider starting ERT, it would be best to go to a doctor experienced with prescribing ERTs for lysosomal storage diseases so that you can talk about the pros and cons of beginning ERT. There are other treatments for Pompe disease that are being studied in clinical trials (e.g., gene therapy, combination therapy).

In addition to enzyme replacement therapy for Pompe disease, it is important to follow up regularly with several different medical specialists to manage different symptoms or possible symptoms of Pompe. First, it is recommended that everyone with Pompe disease be followed by a doctor who is knowledgeable about lysosomal storage diseases and/or Pompe disease. This may be a medical geneticist (genetics doctor), a neurologist (nerve doctor) in a Muscular Dystrophy Association clinic, or other doctor who has followed similar patients. Anyone with Pompe disease should follow regularly with a cardiologist (heart doctor) who may recommend an echocardiogram (ultrasound of the heart) and/or electrocardiogram (ECG; study of the heartbeat). A pulmonologist (lung/breathing doctor), gastroenterologist (GI; doctor for eating and swallowing issues), or an orthopedic surgeon (bone doctor) may also be needed depending on the symptoms. Regular physical, occupational, and speech therapy can be very helpful in helping to keep the muscles working longer.

If someone has a family member affected with Pompe disease, prenatal testing can be done to look for Pompe disease in a pregnancy. If the specific changes in the GAA gene are known in the family, two tests are available during pregnancy. The first is called chorionic villus sampling (CVS) which is usually done between 10 to 14 weeks of pregnancy. It involves inserting a needle through the mother's belly or cervix while an ultrasound is being done. The needle takes a little bit of the placenta, which is made from the same cells as the baby. The placental cells can be grown in a laboratory and tested to see if the placenta/baby has the two changes found in the family to cause Pompe disease. The second test is called amniocentesis (amnio) and is usually done between 15 and 20 weeks of pregnancy. With this test, a needle is inserted into the mother's belly while an ultrasound is being done and takes a little bit of the amniotic fluid from around the baby. There are cells in the fluid that have washed off the baby that can be grown in a laboratory. These cells are tested for the 2 GAA changes from the family. Both CVS and amnio are considered almost 100% accurate but carry a small risk of miscarriage between 1 in 200 to 1 in 500, or between 0.2% to 0.5%.

If you have Late onset Pompe disease (LOPD), there is a possibility that your full brothers and sisters also have Pompe disease. They should all be tested by either enzyme testing of the acid maltase enzyme or by testing the GAA gene for the 2 changes found in you (known mutation DNA testing). Both tests are blood tests. If your full brothers and sisters are not affected with Pompe, there is a 2 in 3 (66%) chance that they are carriers of one copy of the non-working gene and one copy of the working gene. As a carrier, they have no symptoms but can pass on the non-working gene to their children. The known mutation testing will find carriers, but the enzyme testing will not. If you want to find out who are carriers in the family, make sure to talk to your doctor about DNA known mutation testing.

For more information about genetic testing options, including panel testing, go to GeneTests.org.

There are several things to consider when thinking about going on enzyme replacement therapy (ERT) for late onset Pompe disease (LOPD). Currently, there is only one FDA approved medication for Pompe disease: alglucosidase alfa (Lumizyme®) made by Sanofi Genzyme. Lumizyme has been shown to be effective at reducing glycogen stores in the heart muscles (cardiac muscle) but works less well in the skeletal muscle because skeletal muscles do not have as many receptors to take up the enzyme. (Think of it like buckets needed to take water from a river to bring it in the house. Without the buckets, you can't get the water from the river to the house. Cardiac muscle has lots of buckets, while skeletal muscle has less). Still, it slows progression of the disease even in the skeletal muscle so that people with LOPD can use their muscles longer.

ERT is very expensive, but health insurance usually covers most of the cost of ERT. Many times, the remaining cost of ERT can be covered by co-pay assistance programs. The ERT infusions take several hours and must be done every 2 weeks for the rest of your life. It is important to discuss the benefits and limitations of ERT with a physician knowledgeable about Pompe disease and ERT.