Glycogen storage disease type VI (GSD VI) is a type of glycogen storage disease caused by a deficiency in liver glycogen phosphorylase or other components of the associated phosphorylase cascade system.

[3] The scope of GSD VI now also includes glycogen storage disease type VIII,[2] IX[2] (caused by phosphorylase b kinase deficiency) and X[2] (deficiency protein kinase A).

Patients generally have a benign course, and typically present with hepatomegaly and growth retardation early in childhood.

[4] Because symptoms of GSD6 are generally mild, the disorder usually requires no treatment other than to avoid prolonged periods without eating.

Levels of blood glucose should be monitored to make sure that the diet is working correctly.