Pompe disease, or glycogen storage disease type II, is a rare autosomal recessive disorder caused by mutations in the gene that encodes for α-glucosidase. Presentation in infancy is associated with respiratory failure, cardiomyopathy, and severe muscle weakness. Juvenile- or adult-onset cases typically present with proximal muscle weakness and are associated with respiratory insufficiency or exertional dyspnea. Treatment, until recently, was focused on supportive measures, and infants diagnosed with Pompe disease usually died within the first year of life. The recent development of recombinant α-glucosidase has dramatically improved the life expectancy and quality of life of infantile-onset disease with improvements in respiratory and motor function observed in juvenile- or adult-onset cases. This review focuses on the presentation, pathogenesis, diagnosis, and treatment recommendations for Pompe disease in this new era of enzyme replacement therapy.