What is Pompe disease?

There are two types of Pompe disease:

• The ‘classic’ form, which begins within a few months after birth. Babies with this type of Pompe disease have general muscle weakness, including weakness of the respiratory muscles and heart muscle (cardiomyopathy)
  Without treatment with Enzyme Replacement Therapy (ERT) these children die within the first year of life. 
• The ‘non-classic’ form which can have its onset as well during the childhood years as in adult life. This form of the disease is mainly characterized by weakness in the skeletal and respiratory muscles, which ultimately leads to wheelchair and/or ventilator dependency. The heart is almost never involved.  

The earlier in life Pompe disease manifests itself, the more severe are the consequences. 

Pompe disease is a rare disorder which occurs at one in every 40.000 births. At this moment there are 200 patients in the Netherlands known to have Pompe disease (approx. 30 patients with the 'classic form' and 170 patients with the 'non-classic' form.) 

Pompe disease is caused by a disturbed metabolism in the skeletal, respiratory and heart muscle, due to the lack of the enzyme called acid alpha-glucosidase (GAA). This enzyme breaks down glycogen in the body cells and converts it into glucose ('energy'). Patients missing the GAA enzyme have an accumulation of glycogen in the muscle cells, which causes damage to the muscle cells and ultimately making the muscles weaker. 

The most common symptom in Pompe disease is muscle weakness, especially in the legs and respiratory muscles. In babies and young infants the heart muscle also usually weakens. Due to muscle weakness, patients with Pompe disease often suffer from fatigue and pain.

The symptoms and problems experienced by patients with Pompe disease are related to the two different types of the disease.

• In the classic form babies suffer from noticeable muscle weakness, causing the inability to, for example, hold up their heads, to rollover on their own and having feeding problems (sucking / swallowing). On top of this, they experience shortness of breath and are susceptible to respiratory tract infections. Their tongue, heart and liver are enlarged.  
• In the non classic form respiratory and mobility problems develop more slowly. In children there is a delay in the development of motor skills. In adults, the first reported symptoms are usually weakness in the legs and hips causing them to develop a wadling gait, muscle and back pain and to fall a lot. The muscles in the shoulders and upper arms can also become affected. In children and young people a curvature of the spine often occurs. Patients have troubles walking the stairs and over time become wheelchair and ventilator dependent due to increasing muscle weakness.    

Pompe disease is diagnosed based on symptoms of muscle weakness combined with the results of additional tests. In some of the cases a delay in diagnosis can occur due to fact that many symptoms are similar to other medical conditions such as SMA, Becker muscular dystrophy, Duchenne muscular dystrophy, polymyositis and limb-girdle muscular dystrophy. Blood and DNA testing, and in some cases a skin or muscle biopsy, are needed to make a decisive diagnosis.     

• Blood tests are done to measure the enzymatic activity of acid alpha-glucosidase (GAA). 
• A skin biopsy is done if the results of the blood test are inconclusive. In cultured skin cells (fibroblasts) the enzymatic activity of acid alpha-glucosidase (GAA) can be measured.   
• A muscle biopsy is being done to detect abnormalities in the muscle tissue. Under local anesthesia a piece of muscle tissue will be removed and studied under a microscope. The muscle biopsy shows so-called 'vacuoles' in the muscle fibers in which the storage of glycogen can be seen.      
• Through DNA genetic testing it can be established which variant in the GAA gene is causing the disease. The GAA-gene is responsible for the missing enzyme that breaksdown glycogen. To get certaintity during pregnancy, chorionic villus sampling (CVS) and amniocentesis can be done. In the future, neonatal screening may also be able to detect the disease so that babies with the classic form of Pompe disease can start treatment as soon as possible.  

At this moment, the only effective treatment for Pompe disease is enzyme replacement therapy with the medicine called Myozyme. This is a life long treatment. Enzyme replacement therapy reduces the symptoms and improves or stablizes the physical health of the patient. In children with the classic form of Pompe disease there is a notable effect on survival. This is because of improvement of the heart function.  

In the Netherlands, patients with Pompe disease receive the missing enzyme through intravenous (IV) infusion in the Pompe Center at the Erasmus MC University Medical Center in Rotterdam. Depending on which type of Pompe disease the patient has, enzyme replacement therapy is given every week ('classic' type) or every other week ('non-classic' type). Patients who are treated at the hospital for a longer period of time, can also receive enzyme replacement therapy at home under the supervision of Erasmus MC University Medical Center. 

Next to this, other supportive treatments are available to control the symptoms in daily life. E.g. physiotherapy, occupational therapy, speech therapy, nutritional support (tube feeding) and respiratory support. 

Research on different ways to slow down and ultimately cure Pompe disease is being done at the Pompe Center and also internationally. 

At the Pompe Center, neurologist are the main practicioner for adult Pompe patients and the pediatrician and child neurologists are the main practicioners for children.

Next to the main practicioner, nurses, nurse specialists, dieticians, physiotherapists, psychologists and social work are closely involved in the care for Pompe patients. Sometimes, the patients show symptoms which fall under the specialism of another department. E.g. an ENT specialist for swallowing problems and a pulmonologist for respiratory problems. Different specialism can be involved in the care for Pompe patients. The main practicioner, also known as the coordinator, keeps an overview and monitors the patients during treatment.