Mitochondrial electron transport chain defect presenting as hypoglycemia

A profoundly deaf female infant was found to have hypoglycemia and lactic acidemia after an episode of decreased oral intake and vomiting. Electron transport chain (ETC) enzyme studies revealed a combination defect of complexes I, III, and IV in liver but not in skeletal muscle. This case highlights the fact that defects of the ETC are clinically highly heterogeneous and should be considered with hypoglycemia and lactic acidosis in the absence of a glycogen storage disorder. Moreover, ETC defects can occur with a biochemical profile suggestive of a fatty acid oxidation disorder.