A patient with pernicious anemia lacks intrinsic factor due to autoimmune destruction of gastric parietal cells. At which anatomical site does intrinsic factor-mediated absorption of vitamin B12 occur?

• A Duodenum
• B Jejunum
• C Colon
• D Terminal ileum ✓

Explanation

Vitamin B12 bound to intrinsic factor is absorbed via cubilin receptors in the terminal ileum. This is why ileal resection or disease causes B12 deficiency. The duodenum and jejunum absorb most other nutrients including iron, folate, and fat-soluble vitamins. Pernicious anemia results from autoimmune gastritis destroying parietal cells that produce intrinsic factor.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.