Disorders Involving Energy Production

1. Glycogen storage disorders. Patients classically present with enlarged liver and subsequent preprandial hypoglycemia and may manifest acute hypoglycemia with intercurrent illness or fast. Lactic acidosis from the chronic energy depletion state provides a source of energy for the brain, and often the hypoglycemia goes unnoticed until an illness occurs. Long-term sequelae can include liver adenomas, progressive renal insufficiency, and gout.

2. Fatty acid oxidation (FAO) defects. Involve enzymatic defects in fatty acid 0-oxidation. In fasting states, when glycogen stores are depleted, fats must be mobilized for energy production. If 0-oxidation is impaired, hypoglycemia develops with relative hypoketosis or aketosis. Metabolites are organic acids, with resultant positive gap acidosis, and may have a direct toxic effect on the CNS. Myopathy, cardiomyopathy, retinopathy, and other systemic manifestations can occur over time in some patients with FAO defects.

3. Primary lactic acidosis. Typically thought of as disorders of gluconeogenesis, Krebs cycle, or the electron transport chain. Patients often present acutely with positive gap acidosis due to lactate or pyruvate, or both. Hypoglycemia is variable.

E. Structural cardiac defects. Suggested by history and physical exam.

F. Trauma. Altered mental status or vomiting can occur with head or abdominal trauma.

G. Toxic Exposure (eg, organophosphates).

H. Dehydration. From intercurrent GI illness or formula intolerance.

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