Pompe disease is a rare inherited neuromuscular disorder that causes progressive muscle weakness in people of all ages. Part of the family of hereditary diseases known as lysosomal storage disorders, Pompe disease is caused by a defective gene that results in a deficiency of an enzyme called acid alpha-glucosidase (GAA). The absence of this enzyme results in excessive buildup of a substance called glycogen, a form of sugar that is stored in a specialized compartment of muscle cells throughout the body. Pompe disease is very rare and is estimated to affect between 5,000 and 10,000 people worldwide.
Lysosomal storage disorders (LSDs) are a group of rare genetic conditions caused by enzyme deficiencies. In a lysosomal storage disorder, certain structures in cells, called lysosomes, have trouble breaking down specific complex fatty molecules. As a result, the lysosomes fill up with these undigested molecules, impairing the cell’s ability to function properly.
Although the genetic defect that causes Pompe disease is always present at birth, symptoms may first show up at any time from infancy through adulthood. When symptoms first appear in infancy (during the first few months of life), Pompe disease generally progresses very rapidly and is almost always fatal by the age of one year, usually from heart and/or breathing failure. The very rapid disease progression seen in infants makes prompt diagnosis particularly important so that disease management can begin as early as possible.
When symptoms first appear in childhood or adulthood, symptoms may progress slowly over many years or very rapidly. Because the course of the disease is hard to predict, careful monitoring is important to address changes in health status as they arise.
Signs & Symptoms
Pompe disease is described as a progressive disease because it gets worse over time. The progressive nature of Pompe disease is a result of its underlying cause: the ongoing buildup of glycogen inside muscle cells. As excess glycogen continues to accumulate, it interferes with normal cell function and causes continuous damage to cells, resulting in worsening muscle weakness that can affect movement, breathing, and, in infants, heart function.
Although the effects of Pompe disease vary from patient to patient, some broad generalizations can be made.
- Infants typically have extreme muscle weakness and a “floppy” appearance. X-rays usually reveal a greatly enlarged heart. Other symptoms include breathing difficulties, trouble feeding, and a failure to meet developmental milestones such as rolling over and sitting up.
- Children and adults tend to have greater variety in their symptoms, often including weakness of the leg and hip muscles, leading to difficulties with mobility, as well as breathing difficulties. Older patients rarely have the heart problems typical in infants.
Juan, Pompe Disease
A complex and rare disorder, Pompe disease can be challenging to identify for several reasons. Because the disorder is so rare, many doctors have not encountered it before and may not think to consider it as a possible diagnosis. In addition, many Pompe symptoms are not unique to this disease, and thus it can be easily diagnosed as other, more common diseases. Because of its progressive nature—it always worsens over time—it is important to diagnose Pompe disease as early as possible, so that appropriate patient care can begin promptly.
After examining a patient’s symptoms and reviewing the results of several different tests, doctors may ultimately come to suspect Pompe disease. A conclusive way to confirm this diagnosis is by measuring the activity of the GAA enzyme, which is always lower than normal in people with Pompe disease. The test used for this is called an enzyme assay, which can be performed with a simple blood test.
Consult your doctor if you believe you or someone you know has exhibited symptoms of Pompe disease.