<unk>  is caused by genetic defects in the gene that codes for liver glycogen synthetase (GYS2), which is located on chromosome band 12p12.2. Glycogen synthetase catalyzes the rate-limiting reaction for glycogen synthesis in the liver by transferring glucose units from uridine 5'-diphosphate (UDP)-glucose to a glycogen primer. Its action is highly regulated by a mechanism of phosphorylation and dephosphorylation and modulated by counter-regulatory hormones including insulin, epinephrine, and glucagon. Mutations in the gene for liver glycogen synthetase (GYS2, 138571) result in decreased or absent activity of liver glycogen synthetase and moderately decreased amounts of structurally normal glycogen in the liver. Mutational studies of patients with<unk>  do not demonstrate correlations between genotype and phenotype. 3 A different gene (GYS1, 138570) encodes muscle glycogen synthetase, which has normal activity in patients with<unk> A.
Glycogen storage disease type 0
Glycogen storage disease type III
Glycogen storage disease type I
Glycogen storage disease type II
Glycogen storage disease type IV
Glycogen storage disease type V
Glycogen storage disease type VI
Glycogen storage disease type IX