Typically, patients demonstrate hypoglycemia and ketosis with reference range lactate and alanine levels approximately 5-7 hours after fasting. A glucagon challenge after the fast fails to elicit the expected rise in plasma glucose. Reference range levels of lactate and alanine are seen. By contrast, a glucagon challenge after a meal causes hyperglycemia with decreased levels of plasma lactate and alanine. Oral loading of glucose, galactose, or fructose results in a marked rise in blood lactate.
Definitive diagnosis requires a liver biopsy for microscopic analysis and enzyme assay.
Evidence of increased fat accumulation in the liver may be observed, similar to other forms of glycogen storage disease. Electron microscopic analysis of liver sections shows normal glycogen structure. Muscle glycogen stores are normal. Management includes nutritional management and avoidance of fasting hypoglycemia. Refer the patient to a dietitian experienced with GSD and the management of disorders with increased risk of hypoglycemic episodes.