ERT is now commercially available for a number of LSDs, including Pompe disease (also known as “type II glycogen storage disease”), a severe neuromuscular disorder caused by a partial or total loss of activity of the lysosomal enzyme acid alpha-glucosidase (GAA), which is solely responsible for the hydrolysis of glycogen to glucose in the lysosome. This evidence concerns the gene GAA and Glycogen storage disease due to glycogenin deficiency.