Late onset Pompe disease (LOPD) is a systemic genetic metabolic disease involving skeletal and respiratory muscles, caused by a deficiency of acidic alpha-glucosidase (GAA enzyme) in the lysosomes. Respiratory failure is a major cause of morbidity and mortality in patients with LOPD, and we recently held a meeting of patients with late-onset Pompe disease to perform a respiratory function observation. We studied the pulmonary function of 11 patients with late-onset LOPD. The patients’ ages ranged from 13 to 33 years, with a median age of 24 years. Four of the patients required nocturnal BiCAP non-invasive positive pressure assisted ventilation. The tests included force spirometry (FVC) in the standing and prone positions, first second force expiratory volume (FEV1), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP) and peak cough flow rate (CPF). RESULTS: The mean FVC of patients in the standing position was 43.7% (21.9-115.4%). the FEV1 was 42.3% (21.9-113.2%). the FEV1/FVC ranged from 80.17-97.22 and the FVC decreased from the standing to the prone position by 19.84% (2.68-52.67%). the mean of the measured/predicted MIP values was 33.8% ( The mean of measured/predicted MEP values was 40.8% (13.9-109.1%). CONCLUSION: Respiratory dysfunction in patients with late-onset LOPD is mainly caused by restrictive ventilation disorders, with inspiratory muscle weakness dominated by the diaphragm being more prominent. Assisted breathing should be performed early.