A 58-year-old woman presents with fatigue and numbness of the feet. CBC shows Hb 9.2 g/dL, MCV 118 fL, and hypersegmented neutrophils. Serum vitamin B12 is low. Which additional finding would most strongly support pernicious anemia as the underlying cause?

• A Elevated serum homocysteine with normal methylmalonic acid
• B Low serum folate with elevated LDH
• C Antibodies against intrinsic factor in the serum ✓
• D Ringed sideroblasts on bone marrow iron stain

Explanation

Pernicious anemia results from autoimmune destruction of gastric parietal cells, producing intrinsic factor deficiency and impaired ileal absorption of C12. Anti-intrinsic factor antibodies are highly specific for the condition and confirm the etiology. Option A actually describes isolated folate deficiency, since methylmalonic acid rises only when C12 is deficient because MMA conversion requires C12-dependent methylmalonyl-CoA mutase.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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