• Every gene in a person’s body comes as a pair. One of this pair comes from their mother, the other comes from their father. The combination of ‘GAA genes’ passed to them from their parents determines whether a given person will have Pompe disease:

    • If both ‘GAA genes’ in the pair are normal, the person will not have Pompe disease
    • If both ‘GAA genes’ in the pair are faulty, the person will have Pompe disease 
    • If one ‘GAA gene’ is normal and the other is faulty, the person will be a ‘carrier’ of Pompe disease

    Carriers do not have Pompe disease themselves, but they do have a faulty ‘GAA gene’ and may pass this on to their children. Although Pompe disease carriers have one faulty ‘GAA gene’, their other normal ‘GAA gene’ enables production of GAA, so harmful build-up of glycogen doesn’t happen. Even though the amount of GAA that they make is usually lower than normal, carriers have no symptoms of Pompe disease.