Pompe disease is a rare lysosomal storage disorder whose main manifestation is muscle weakness.
The hallmark of lysosomal storage disorders is the lack of functional enzymes that can break down cells’ fats or carbohydrates.
Mutations of the GAA gene are the cause of Pompe disease. The abnormalities lead to the production of a faulty version of the acid alpha-glucosidase enzyme. This enzyme is responsible for breaking down a complex sugar molecule called glycogen into a form that cells can use to generate energy.
When the enzyme is faulty, damaging levels of glycogen build up inside cells, leading to the symptoms of the disease.
How many people have Pompe disease?
Experts estimate that 5,000 to 10,000 people have Pompe disease worldwide.
Because it is so rare, diagnosing it can be a challenge for doctors. This means that the number of people with the disorder may be higher than the estimates.
Geographical differences
The number of people with Pompe disease varies greatly by region of the world.
A mutation screen in newborns suggested that it affects 1 in 40,000 people in the Netherlands. Many experts believe this to be an underestimation because the screening included only the three most common Pompe mutations — those accounting for 63% of the cases.
Pompe is much less common in Australia than Holland, with an incidence of one in 145,000 people. It is even rarer in Portugal, with 1 in 600,000 newborns diagnosed with it, based on acid alpha-glucosidase enzyme activity tests and genetic tests.
Incidence of infantile-onset Pompe disease
A third of Pompe patients are infants. The infantile-onset form of the disease is caused by mutations that lead to the production of less than 2% of functional acid alpha-glucosidase enzyme.
The incidence of infantile-onset Pompe disease varies between regions and ethnic groups. The frequency is estimated at 1 in 138,000 people in the Netherlands. In some countries, including China and Taiwan, and among certain ethnic populations, such as African Americans, the incidence is as high as 1 in 14,000 people.
Incidence of late-onset Pompe disease
Late-onset Pompe disease is a milder form. Patients have functional acid alpha-glucosidase enzyme levels of between 2% and 40%, leading to slower glycogen buildup. The severity of symptoms and age of onset vary greatly from patient to patient.
Other than one study in the Netherlands estimating that 1 in 57,000 adults has late-onset Pompe disease, there is no information on its incidence.
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