Glycogen storage disease is any one of several inborn errors of metabolism that result from enzyme defects that affect the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types.

There are eight diseases that are commonly considered to be glycogen storage diseases:

• GSD type I: glucose-6-phosphatase deficiency,von Gierke's disease
• GSD type II: acid maltase deficiency,Pompe's disease
• GSD type III: glycogen debrancher deficiency
• GSD type IV: glycogen branching enzyme deficiency, Andersen disease
• GSD type V: muscle glycogen phosphorylase deficiency, McArdle disease
• GSD type VI: liver phosphorylase deficiency
• GSD type VII: muscle phosphofructokinase deficiency
• GSD type IX: phosphorylase kinase deficiency

• GSD type 0: glycogen synthase deficiency

Although glycogen synthase deficiency does not result in storage of extra glycogen in the liver, it is often classified with the GSDs because it is another defect of glycogen storage and can cause similar problems.