GI System MCAT Practice Question
A 28-year-old woman presents with a 6-month history of chronic diarrhea, abdominal bloating, and progressive weight loss despite adequate oral intake. She reports fatigue and numbness in her feet. Laboratory studies show iron-deficiency anemia (hemoglobin 9.2 g/dL, MCV 71 fL), hypoalbuminemia (2.8 g/dL), and elevated tissue transglutaminase (tTG) IgA antibodies. Upper endoscopy with duodenal biopsy reveals villous atrophy with increased intraepithelial lymphocytes. The biopsy findings are consistent with celiac disease, in which autoimmune-mediated intestinal damage occurs via tTG modification of gliadin peptides and their presentation on HLA-DQ2 molecules to CD4+ T cells. Which of the following best explains the patient's malabsorption?
Answer choices
- ADecreased intestinal epithelial surface area due to villous flattening reduces the capacity for nutrient absorptionCorrect answer
- BTissue transglutaminase directly hydrolyzes dietary proteins into amino acids that cannot be absorbed
- CCD4+ T cell infiltration increases mucus production, creating a thicker unstirred water layer that impairs nutrient diffusion
- DHLA-DQ2 molecules bind to nutrient transporters on the apical epithelial membrane, blocking their function
- EInflammation-induced increased intestinal permeability allows absorbed nutrients to leak back into the intestinal lumen
- FGliadin peptides competitively inhibit sodium-glucose linked transporter 1 (SGLT1) at the brush border
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