fast. Imaging Studies Skeletal radiography may reveal osteopenia. Other Tests Evaluation of a patient with suspected glycogen-storage disease type 0 requires monitored assessment of fasting adaptation in an inpatient setting. Patients typically have hypoglycemia and ketosis, with lactate and alanine levels in the low or normal part of the reference range approximately 5–7 hours after fasting. A glucagon tolerance test may be needed if the fast fails to elicit the expected rise in plasma glucose. Lactate and alanine levels are in the reference range. By contrast, a glucagon challenge test after a meal causes hyperglycemia, with increased levels of plasma lactate and alanine. Oral loading of glucose, galactose, or fructose results in a marked rise in blood lactate levels. Procedures Liver biopsy for microscopic analysis and enzyme assay is required for definitive diagnosis. Diagnosis may include linkage analysis in families with affected members and sequencing of the entire coding region of the GSY2 gene for mutations. Histologic Findings Histologic analysis of liver tissue demonstrates moderately decreased amounts of periodic acid-Schiff (PAS)–positive, diastase-sensitive glycogen stores. Evidence of increased fat accumulation in the liver may be observed, as in other glycogen-storage diseases. Electron microscopic analysis of liver sections shows normal glycogen structure. Muscle glycogen stores are normal. Differential Diagnoses Acute Hypoglycemia Fructose 1-Phosphate Aldolase Deficiency (Hereditary fructose intolerance). Types There are two types of glycogen storage disease type 0 to be considered, they are: Glycogen storage disease due to liver glycogen synthase deficiency Glycogen storage disease due to muscle and heart glycogen synthase deficiency Treatment The goal for treatment of Glycogen-storage disease type 0 is to avoid hypoglycemia. This is accomplished by avoiding fasting by eating every 1–2 hours during the day. At night, uncooked corn starch can be given because it is a complex glucose polymer. This will be acted on slowly by pancreatic amylase and glucose will be absorbed over a 6-hour period. Epidemiology The overall frequency of glycogen-storage disease is approximately 1 case per 20,000–25,000 people. Glycogen-storage disease type 0 is a rare form, representing less than 1% of all cases. The identification of asymptomatic and oligosymptomatic siblings in several glycogen-storage disease type 0 families has suggested that glycogen-storage disease type 0 is underdiagnosed. Mortality/Morbidity The major morbidity is a risk of fasting hypoglycemia, which can vary in severity and frequency. Major long-term concerns include growth delay, osteopenia, and neurologic damage resulting in developmental delay, intellectual deficits, and personality