Anemias: The Daily PANCE Blueprint
A 68-year-old woman presents with several months of progressive fatigue, exertional dyspnea, and a "pins and needles" sensation in her feet. Her past medical history is significant for Crohn's disease, which required a small bowel resection involving the terminal ileum five years ago. On physical examination, she is pale and has diminished vibratory sense and proprioception in her lower extremities. A complete blood count is ordered. Which of the following findings would be most expected in this patient?
A. Microcytic, hypochromic red blood cells with low ferritin
B. Normocytic, normochromic red blood cells with a high reticulocyte count
C. Macrocytic red blood cells with hypersegmented neutrophils
D. The presence of Heinz bodies and bite cells on peripheral smear
E. Macrocytosis with a normal methylmalonic acid level
Answer and topic summary
The answer is Macrocytic red blood cells with hypersegmented neutrophils
This patient’s clinical presentation, including macrocytic anemia and neurological symptoms, in the context of a prior terminal ileum resection, is highly suggestive of vitamin B12 (cobalamin) deficiency. The terminal ileum is the primary site for the absorption of vitamin B12 complexed with intrinsic factor. Its resection leads to malabsorption and eventual deficiency. The classic hematologic findings of vitamin B12 deficiency are a macrocytic anemia (mean corpuscular volume [MCV] > 100 fL) and the presence of hypersegmented neutrophils (>5 lobes) on the peripheral blood smear. The neurological manifestations, such as paresthesias and loss of proprioception/vibratory sense, are due to defective myelin synthesis affecting the dorsal and lateral spinal columns. Diagnosis is confirmed with a low serum vitamin B12 level and elevated levels of both methylmalonic acid (MMA) and homocysteine. Treatment requires lifelong parenteral or high-dose oral vitamin B12 supplementation.
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