Pompe Disease

What is Pompe disease?

Pompe disease is a type of glycogen storage disease, a genetic condition in which a complex sugar called glycogen builds up in your body’s cells. The disease results from the deficiency of a digestive enzyme called acid alpha-glucosidase (GAA). GAA normally breaks down complex sugars in your body.

Other names for the condition include:

• Pompe’s disease.
• Acid maltase deficiency.
• Glycogen storage disease type II (GSD2).

Providers also refer to Pompe disease (pronounced “pom-pay”) as a lysosomal storage disease. Lysosomes are small compartments inside your cells that hold and recycle certain substances. Enzymes such as GAA (or acid maltase, hence the name acid maltase deficiency) help break down these substances.

A lack of this enzyme causes glycogen to build up within the lysosomes. This buildup occurs in the cells of your organs and tissues, especially your heart and skeletal muscles, causing them to break down.

Types of this condition

Researchers have described two main types of Pompe disease. They differ based on your age of onset and the severity of your symptoms.

Infantile-onset

People who develop Pompe disease as infants are typically the most severely affected. A complete lack of, or very little, acid alpha-glucosidase enzyme causes this type of Pompe disease. Your baby may not have any signs of the condition at birth, but symptoms start within the first year of life, most often around 4 months of age.

Symptoms include severe muscle weakness, an enlarged liver and an enlarged heart due to cardiomyopathy. The progression of the disease will happen quickly. Without treatment, babies usually die of heart or respiratory failure between 1 and 2 years of age.

Late-onset (juvenile or adult-onset)

Symptoms of late-onset Pompe disease can appear at any age — before 1 year of age but without an enlarged heart (which distinguishes it from infantile-onset), later in a child’s life, during adolescence or in adulthood. People with late-onset type have a reduced amount of acid alpha-glucosidase. This type is usually milder, and progression happens at a slower pace. But it depends on the age of onset. Children who develop symptoms are usually more severely affected.

Symptoms include muscle weakness (myopathy) that can lead to breathing issues, but the disease is unlikely to affect your heart. Without treatment, people usually die of respiratory complications.

How common is Pompe disease?

Pompe disease is a rare genetic condition. In the United States, it affects about 1 in every 40,000 people.

What are the symptoms of Pompe disease?

Pompe disease causes progressive muscle weakness, especially in the skeletal muscles of your hips, legs, shoulders, arms and diaphragm. Babies may have poor muscle tone, or “floppy infant syndrome” (hypotonia). In addition, enlargement of your heart (cardiomegaly), liver (hepatomegaly) and tongue (macroglossia) may occur.

Other infantile Pompe disease symptoms may include:

• Trouble gaining weight and growing at the expected rate (failure to thrive).
• Difficulty breathing.
• Feeding issues.
• Respiratory infections.
• Hearing problems.

Late-onset Pompe disease symptoms may be milder and progress slower. However, they can still cause severe weakness and breathing (respiratory) issues. Symptoms may include:

• Legs and trunk get steadily weaker.
• Increasing difficulty walking.
• Muscle pain over a large area.
• Loss of the ability to exercise.
• Falling often.
• Frequent respiratory infections.
• Shortness of breath (dyspnea) when you push yourself.
• Headaches in the morning.
• Tiredness during the day.
• Unintended weight loss.
• Difficulty swallowing (dysphagia).
• Irregular heartbeat (arrhythmia).
• Increased difficulty hearing.

What causes Pompe disease?

Mutations in the GAA gene cause Pompe disease. The GAA gene is responsible for making an enzyme called acid alpha-glucosidase. Your body uses this enzyme to break down glycogen, a complex form of sugar.

Your body normally converts glycogen into glucose, which it uses for energy. Acid alpha-glucosidase works within compartments within your cells called lysosomes. Lysosomes are like recycling centers within your cells. The enzymes help break down substances and send them out to your body to do something new, like provide energy.

If you have Pompe disease, mutations in the GAA gene cause a reduced or complete lack of acid alpha-glucosidase. Without this enzyme, your body can’t break down glycogen effectively. The glycogen builds up in your lysosomes, causing severe muscle damage, which leads to the symptoms of the disease.

You inherit the condition in an autosomal recessive manner, which means both of your parents have to pass on copies of the mutated gene to you. Each parent is a carrier of Pompe disease, but they usually don’t show symptoms of the condition.

What are the complications of Pompe disease?

Without treatment, infantile-onset Pompe disease is fatal early in childhood. Many people with Pompe disease have breathing (respiratory) and heart problems. Almost all people with the disease have muscle weakness. Most people will need oxygen support and mobility assistance at some point in their lives.

How is Pompe disease diagnosed?

Your healthcare provider will perform a physical exam and ask about your biological family history. Your provider will take a blood sample to analyze an enzyme called creatine kinase. This test checks for signs of muscular damage. A more definitive way is to check the amount of enzyme activity in your blood. Your provider can also use genetic testing to study the GAA gene in your body.

You may also have tests such as:

• Pulmonary function tests: Breathing tests that measure lung capacity.
• Electromyography: A test that measures how well your muscles work.
• Heart studies: These may include an electrocardiogram (EKG) and an echocardiogram (echo).
• Sleep studies: These tests record specific body functions while you sleep.

How is Pompe disease treated?

Pompe disease treatment includes enzyme replacement therapy (ERT). Your healthcare provider will give you one of the following medications intravenously (through your vein):

• Alglucosidase alfa.
• Avalglucosidase alfa.

These drugs are genetically engineered enzymes that act like naturally occurring enzymes. They help:

• Decrease heart size.
• Maintain normal heart function.
• Improve muscle function, tone and strength, or at least slow the progression of the disorder.
• Reduce glycogen buildup.

In addition, a team of specialists will treat your individual symptoms and provide supportive care. This team may include:

• Physical, occupational and respiratory therapists.
• Cardiologists.
• Neurologists.

Depending on the severity of your condition, you may need:

• Physical or occupational therapy.
• A feeding tube.
• Mechanical ventilation.

Scientists are currently studying clinical trials of Pompe disease gene therapy. Gene therapy replaces damaged genes with healthy genes, which allows your body to make acid alpha-glucosidase correctly.

How can Pompe disease be prevented?

You can’t prevent Pompe disease because it’s a genetic condition. If you’re pregnant or planning on becoming pregnant, you may want to talk to your provider about genetic counseling.

What is the Pompe disease life expectancy?

Without early detection and treatment, babies with infantile-onset Pompe disease frequently die of respiratory or heart failure.

People with late-onset types of Pompe disease can often live longer, as the disease progresses at a slower rate. However, it depends on the age of onset and severity of the disease. Typically, the later the age of onset, the slower the progression of the condition.

When should I see my healthcare provider?

If you or your child has signs of Pompe disease, you should see your healthcare provider right away. Early diagnosis can greatly improve the quality of life of children and adults with the disorder.

How do I take care of myself or my child with this disease?

If you or your child has Pompe disease, you may want to consider speaking with a psychologist. A psychologist can help you better understand the condition and cope emotionally. Support groups can also put you in touch with people dealing with similar conditions. Many people experience caregiver fatigue or burnout. It’s a common occurrence, but it’s important to take care of yourself as well as your child.

What should I ask my healthcare providers about Pompe disease?

If you or your child receives a Pompe disease diagnosis, consider asking your provider:

• What type of Pompe disease does my child have?
• What’s my child’s life expectancy?
• What specialists will we need to see?
• How often should we see these specialists?
• How can I keep my child comfortable?
• Should other family members get genetic testing?
• How can I best learn to cope with Pompe disease?