Vitamin B12 Deficiency

Stephan Moll, M.D.

N Engl J Med 1996; 335:323August 1, 1996

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Figure 1 A 72-year-old man with a several-week history of fatigue, loss of appetite, and feeling feverish presented at the hospital with severe pallor and signs of left and right ventricular failure. Neurologic examination disclosed poor short-term memory and decreased sense of vibration in the legs.

An electrocardiogram showed changes consistent with the presence of cardiac ischemia. The hemoglobin level was 3.7 g per deciliter, with a mean corpuscular volume of 103 μm³, a white-cell count of 3200 per cubic millimeter, and a platelet count of 57,000 per cubic millimeter. The peripheral-blood film showed the typical changes of vitamin B₁₂ deficiency: hypersegmentation of neutrophils, marked anisocytosis, poikilocytosis with some large oval erythrocytes (megalocytes; thin arrow), and basophilic stippling (thick arrow). The serum vitamin B₁₂ level was 8 pg per milliliter (6 pmol per liter; normal, >200 pg per milliliter [148 pmol per liter]), and a bone marrow biopsy showed marked megaloblastic changes consistent with the diagnosis of vitamin B₁₂ deficiency. Although the mean corpuscular volume was very low for pure vitamin B₁₂ deficiency of this severity and might have suggested an additional hematologic problem, most notably iron deficiency, no other abnormality was identified.

With parenteral vitamin B₁₂ treatment, the patient's blood counts and mean corpuscular volume returned to normal and the megaloblastic bone marrow changes resolved.

Kim Eagle, M.D.

Stephan Moll, M.D.
Duke University Medical Center, Durham, NC 27710

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