Background: There is paucity of information on the impact of Enzyme Replacement Therapy (ERT) on survival of adult patients with Pompe disease. We assessed whether there is differential mortality in adult patients treated with ERT compared to untreated patients. Methods: Data of 270 patients with a median age of 48 years (range 19-79 years) were collected in an international observational study between 2002 and 2011. Kaplan-Meier survival curves were plotted and multivariate logistic regression analyses were performed.. Results: The ERT-group included 195 patients with 15 deaths and the nontreatment group 75 patients with 26 deaths. Survival was higher for patients on ERT compared to patients never on ERT and for patients with lower compared to higher levels of disease severity. For each level of disease severity (based on wheelchair and ventilator dependency) greater survival on ERT was observed. In logistic regression analyses controlling for age, gender, and national treatment patterns, both treatment with ERT and disease severity were associated with survival. Conclusion: Our results suggest that ERT expands the life span of adult patients even when they are severely affected. Longer follow-up is needed to further elucidate the relationship between ERT, disease severity and survival of adults with Pompe disease. Conflict of Interest declared. Background: The role of infections in IAR during ERT with the exogen protein is still not clear. We report a case of a patient who had been under ERT with Agalsidase Beta for more than four years who had an IAR when presenting an intercurrent infection. Case report: Male, 19 years, on ERT for 4 year. During his 90th infusion, he presented high fever, tremor, skin rash, which was treated with corticosteroids e antihistamine. On that day, even before ERT, he presented cough and rhinorrhea without fever. Acute rhinosinusitis was diagnosed, antibiotics were prescribed and the patient was discharged home. On the next infusion, he had already overcome the rhinosinusitis, was asymptomatic, didn't take any pre-medication and received the ERT without any other IAR. Discussion: The pharmacologic interaction with immune receptors concept (P-I concept) is a recently proposed addition to drug hypersensitivity classification. Infections can incite T lymphocytes to change their link to some drugs and this process may cause adverse reactions. Conclusion: ERT is often complicated by immune responses to the enzymes and the P-I concept must be reminded as an explanation to IAR in patients with infections, because in these cases the use of pre-medication is not necessary. Conflict of Interest declared. 