Pompe Disease — Basic Genetics
Pompe disease is a genetic disorder characterized by a number of signs and symptoms, notably affecting the heart and skeletal muscles. In the U.S, approximately 1 in 40, 000 people have Pompe disease. The main treatment available is called Enzyme Replacement Therapy (ERT).
Types of Pompe Disease
Three types of Pompe disease are recognized:
- Classic infantile-onset — this type manifests very early in infancy, and can be fatal if not treated. Signs and symptoms include muscle weakness, heart defects, and feeding problems.
- Non-classic infantile-onset — this type manifests later in infancy, before the age of one. Muscle weakness, delayed motor skills and breathing problems are among the signs and symptoms. Children with this type also have a shortened life expectancy.
- Late-onset — this type appears any time after the age of one, with signs and symptoms including muscle weakness and breathing problems.
The Gene Involved in Pompe Disease
Pompe disease is the result of a mutation in a gene called glucosidase, alpha; acid (GAA). It located on chromosome 17, and codes for an enzyme called acid alpha-glucosidase. If working correctly, this enzyme turns glycogen into glucose in cells. If the enzyme is impaired, glycogen can build up to excessive levels, resulting in the signs and symptoms of Pompe disease.
Inheritance of Pompe Disease
Pompe disease inheritance in is referred to as ‘autosomal recessive’. People receive two sets of genes: one set from their mother, one set from their father. When a disorder is autosomal recessive, affected people will have received a mutated gene copy from each parent.
People with one mutated gene copy are said to be carriers of the disorder. This means they can pass the gene on to their children, but typically do not experience any signs and symptoms. Where both parents are carriers of the disorder, each pregnancy presents with the following:
- A 1 in 4 (25%) chance of having a child who is affected by Pompe disease.
- A 1 in 2 (50%) chance of having a child who is a carrier of Pompe disease.
- A 1 in 4 (25%) chance of having a child who is not affected.
Genetic Testing and Pompe Disease
The common genetic mutations and enzyme activity levels can both be tested for as part of a Pompe disease diagnosis. Genetic counseling is a possible support option for individuals and/or families concerned about genetic disorders. These professionals are trained to provide information without leading people’s decision-making.