other manifestations of severe fasting hypoglycemia hepatomegaly with abdominal protuberance hyperventilation and apparent respiratory distress due to metabolic acidosis episodes of vomiting due to metabolic acidosis, often precipitated by minor illness and accompanied by hypoglycemia Once the diagnosis is suspected, the multiplicity of clinical and laboratory features usually makes a strong circumstantial case. If hepatomegaly, fasting hypoglycemia, and poor growth are accompanied by lactic acidosis, hyperuricemia, hypertriglyceridemia, and enlarged kidneys by ultrasound, GSD I is the most likely diagnosis. The differential diagnosis list includes glycogenoses types III and VI, fructose 1,6-bisphosphatase deficiency, and a few other conditions (page 5), but none are likely to produce all of the features of GSD I. The next step is usually a carefully monitored fast. Hypoglycemia often occurs within six hours. A critical blood specimen obtained at the time of hypoglycemia typically reveals a mild metabolic acidosis, high free fatty acids and beta-hydroxybutyrate, very low insulin levels, and high levels of glucagon, cortisol, and growth hormone. Administration of intramuscular or intravenous glucagon (0.25 to 1 mg, depending on age) or epinephrine produces little rise of blood sugar. The diagnosis is definitively confirmed by liver biopsy with electron microscopy and assay of glucose-6-phosphatase activity in the tissue and/or specific gene testing, available in recent years. Treatment The primary treatment goal is prevention of hypoglycemia and the secondary metabolic derangements by frequent feedings of foods high in glucose or starch (which is readily digested to glucose). To compensate for the inability of the liver to provide sugar, the total amount of dietary carbohydrate should approximate the 24-hour glucose production rate. The diet should contain approximately 65–70% carbohydrate, 10–15% protein, and 20–25% fat. At least a third of the carbohydrates should be supplied through the night, so that a young child goes no more than 3–4 hours without carbohydrate intake. Once a diagnosis is made, the priority in GSD I treatment is to maintain an adequate blood glucose. Patients aim to maintain a blood glucose above the 72 mg/dL (4.0 mmol/L) cutoff for hypoglycemia. GSD Ib patients have an additional treatment priority relating to neutropenia. Proper management of blood glucose in GSD I is critical in avoiding the more severe effects of high leves of lactic acid and uric acid in the blood, and the development of hepatic adenomas. In the last 30 years, two methods have been used to achieve this goal in young children: (1)