USMLE-Rx Step 1 Qmax Challenge #1161

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USMLE-Rx Step 1 Qmax Challenge #1161A 60-year-old woman with rheumatoid arthritis presents to her doctor with a 2-month history of progressive fatigue. She also reports feeling “wobbly” lately. Physical examination reveals a pulse of 101/min and decreased light touch and vibration sense on her lower extremities. Laboratory studies show a hemoglobin level of 9 g/dL and a mean corpuscular volume of 110 fL. A peripheral blood smear for the patient is shown in the image. On further analysis, methylmalonic acid levels and homocysteine levels are elevated.

This patient’s anemia most likely results from which of the following factors?

A. A vitamin deficiency resulting from medication administered for her rheumatoid arthritis
B. Abnormal neural crest cell migration
C. Antibodies against parietal cells
D. Bacterial overgrowth in the colon
E. Partially occlusive embolus to the superior mesenteric artery


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