A 7-month-old girl of average weight and unremarkable medical and family history presented with chronic osmotic diarrhea and failure to thrive. The onset of symptoms appeared shortly after cereals and fruits were introduced into her diet. As part of the investigation of the gastrointestinal symptoms, a biopsy of the small intestine mucosa was sent to the laboratory for biochemical analysis. Upon receipt of the results, the doctor advised the parents to remove sources of sucrose from her diet.


  1. Which laboratory test performed on the intestinal mucosa is useful in the evaluation of diet-associated osmotic diarrhea?
  2. What is a possible etiology for the condition identified by the test?

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