Glycogen storage disease is a severe genetic disorder of glycogen metabolism, causing glycogen accumulation mainly in the liver. Affected dogs show severe hepatomegaly, fasting hypoglycemia, failure to thrive, and may progress to coma and death. The G6PC gene mutation strongly reduces enzyme activity, disrupting the production of glucose from glucose-6-phosphate. Histologically, the liver shows vacuolated hepatocytes filled with glycogen.
