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 Type II: pups vomit frequently, progressive muscle weakness and poor body condition, esophageal dilation and cardiac enlargement. Death before the age of two years.