Glycogen storage disease type 13 (GSD13), also known as β-enolase deficiency, is an inherited disease of the muscles. The muscles of an affected individual are not able to produce enough energy to function properly, causing muscle weakness and pain. GSD13 is caused by changes (mutations) in the ENO3 gene and is inherited in an autosomal recessive pattern.

Glycogen storage disease type 13 (GSD13) is caused by changes (mutations) in the ENO3 gene. Glycogen is a substance that is stored in muscle tissue and is used as an important source of energy for the muscles during movement and exercise. The ENO3 gene makes a chemical called enolase, which is an enzyme that helps the muscles use glycogen for energy. In GSD13, the ENO3 genes do not work properly such that the body cannot make enolase, and as a result, the muscles do not have enough energy to work properly.

Glycogen storage disease type 13 causes muscle pain (myalgia). Individuals with GSD13 also experience exercise intolerance, which means they have difficulty exercising because they may have muscle weakness and tire easily.

Glycogen storage disease type 13 is diagnosed by taking a sample of muscle tissue (muscle biopsy) to determine if there is enough of the chemical enolase working in the muscle cells. Genetic testing can also be done to look for changes (mutations) in the ENO3 gene.