Glycogen storage disease type 2 (Pompe disease) is an autosomal recessive disorder resulting in acid alpha-glucosidase enzyme deficiency. This causes the buildup of glycogen inside the lysosomes of all tissues, especially within muscle tissue. It is classified as both a glycogen storage disease and a lysosomal storage disease. The causal mutation is found on gene GAA. The disease may first appear in infancy or in later life. Infantile onset occurs within the first few months of life and common findings include hypotonia, cardiomyopathy, cardiomegaly, poor feeding, failure to thrive, and hepatomegaly. Patients with later onset primarily present with skeletal myopathy, weakness, dyspnea, orthopnea, and respiratory failure.

Creatine kinase is elevated in both presentations.