Clinical comments: Glycogen Storage Disease alters the enzyme glucose-6-phosphatase, a key step in the production of glucose, to be deficient. This leads to chronic low blood sugar, liver damage and premature death. Generalised symptoms of Glycogen Storage Disease in dogs includes weakness, chronic low blood sugar, collapse, lethargy, enlarged, liver anorexia. Age of onset from birth/puppyhood. Specific to form I-a is it's generally associated with toy breeds.