Pernicious anemia (243/1700)

A 56yo woman is known case of pernicious anemia. She refuses to take hydroxycobalamin IM as
she is needle shy. She asks for oral medication. Why will oral meds be not effective?

a. Intrinsic factor def
b. Malabsorption
c. Irritated gastric mucosa
d. Lack of gastric acidity





























answer: A

B12 (cobalamin)
• binds to intrinsic factor (IF) secreted by gastric parietal cells
• absorbed in terminal ileum
• total body stores sufficient for 3-4 yr

Pathophysiology of Pernicious Anemia
• auto-antibodies produced against gastric parietal cells leading to achlorhydria and lack of
intrinsic factor secretion
• intrinsic factor is required to stabilize B12 as it passes through the bowel
• decreased intrinsic factor leads to decreased ileal absorption of B12
• may be associated with other autoimmune disorders (polyglandular endocrine insufficiency)
• F:M = 1.6:1; often >60 yr old

Treatment
• vitamin B12 1,000 μg IM monthly for life or 1,000-1,200 μg PO daily if intestinal absorption intact