A 20-year-old male with no significant medical history comes to you with a urine positive for fructose. When asked about his past medical history, he says that he has no significant medical problems. However, his mother told him that he was born with "a problem metabolizing sugar." The patient maintains no dietary restrictions and regularly eats vegetables, fruits, meats, and processed foods. Urine samples show a repeatedly positive copper reduction test, but glucose oxidase dipstick testing is negative. Which of the following enzymes is most likely to be deficient in this patient?

Question

A 20-year-old male with no significant medical history comes to you with a urine positive for fructose. When asked about his past medical history, he says that he has no significant medical problems.  However, his mother told him that he was born with "a problem metabolizing sugar."  The patient maintains no dietary restrictions and regularly eats vegetables, fruits, meats, and processed foods.  Urine samples show a repeatedly positive copper reduction test, but glucose oxidase dipstick testing is negative.  Which of the following enzymes is most likely to be deficient in this patient?

Quizplus · Accepted Answer

Eductional Objective: Unlike hereditary fructose intolerance (aldolase B deficiency) and classic galactosemia (galactose-1-phosphate uridyl transferase deficiency), essential fructosuria (fructokinase deficiency) is a benign disorder. Although affected patients are asymptomatic, their urine will test positive for a reducing sugar due to the presence of unmetabolized fructose.

A 20-Year-Old Male with No Significant Medical History Comes to You