Clinical and animal data both indicate that respiratory muscle function is impaired in Pompe disease. Prigent and colleagues(2012) evaluated trans-diaphragmatic pressure in a large sample ofadults with Pompe disease using gastric and esophageal manometry. Magnetic stimulation of the phrenic nerve was used to evoketrans-diaphragmatic twitch pressure, which provides an indica-tor of diaphragm strength. The study confirmed diaphragmaticweakness, but it should be emphasized that diaphragmatic twitch pressures could also be influenced by conduction impairmentsalong the motor nerve, as well as alterations in the neuromuscular junction. Reductions in expiratory pressures were also observed,and thus expiratory muscle function may also be impaired in Pompe disease (Prigent et al., 2012).