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 adult onset may present with skeletal myopathy; weakness; dyspnea; orthopnea; vascular malformations; oral-gastrointestinal abnormalities such as dysphagia, gastroesophageal reflux, constipation, and dysmotility; cardiovascular abnormalities such as arrhythmias, conduction abnormalities, and cardiomyopathy; cognitive and emotional disturbances such as depression and anxiety; and respiratory failure. Patients rarely survive beyond age 1 year without treatment. The median time from diagnosis to death is 2 months.

Creatine kinase is elevated in both presentations.