A 1-year-old girl is being examined by her physician because of a 3-month history of intermittent vomiting, shakiness, and a failure to thrive. The symptoms began when breast-feeding stopped and fruit and vegetables were added to her diet. Her current size is below the fifth percentile for length and weight. Upon physical examination the physician notes jaundice and hepatomegaly. Intravenous administration of fructose results in hypoglycemia and hypophosphatemia. Deficiency of which of the following hepatic enzymes is the most likely cause of the disorder in this patient?

Question

Quizplus · Accepted Answer

The symptoms and history are consistent with hereditary fructose intolerance, which is caused by a deficiency of aldolase B. This condition leads to the accumulation of fructose-1-phosphate, causing hypoglycemia and hypophosphatemia when fructose is ingested. Hereditary fructose intolerance is a potentially lethal disorder resulting from a lack of aldolase B which is normally present in the liver, small intestine, and kidney cortex. The disorder is characterized by severe hypoglycemia and vomiting following fructose intake. Prolonged intake of fructose by infants with this defect leads to vomiting, poor feeding, jaundice, hepatomegaly, hemorrhage, and, eventually, hepatic failure and death. The hypoglycemia that results following fructose uptake is caused by fructose- 1-phosphate inhibition of glycogenolysis, by interfering with the phosphorylase reaction, and inhibition of gluconeogenesis at the deficient aldolase step. Patients remain symptom free on a diet devoid of fructose and sucrose.

A 1-Year-Old Girl Is Being Examined by Her Physician Because