A 60-year-old man develops numbness of the feet. On physical examination he has lost proprioception in the lower extremities and is noticed to have a wide based gait with a positive Romberg sign. His past medical history includes hypertension, hypothyroidism, and previous gastrectomy for gastric cancer. The peripheral blood smear is shown below.
What is the most likely cause of his symptoms?a. Folic acid deficiency
This is a classic presentation of a patient with vitamin B12 deficiency. This is commonly seen in patients with gastric resection and malabsorption. Patients with gastric resection lose intrinsic factor production from parietal cells. Loss of intrinsic factor leads to decreased absorption of vitamin B12 . Megaloblastic anemia with hypersegmented neutrophils (as seen on this patient’s peripheral blood smear) can be found in both folic acid and vitamin B12 deficiency. Folic acid deficiency does not produce neurologic findings. B12 deficiency may cause a bilateral peripheral neuropathy or degeneration (demyelination) of the posterior and pyramidal tracts of the spinal cord and, less frequently, optic atrophy or cerebral symptoms. Iron deficiency anemia would show micro-cytic and hypochromic red blood cells on peripheral blood smear. Vitamin K deficiency results in a coagulopathy but does not cause neurologic symptoms or hypersegmented neutrophils on peripheral blood smear. Thiamine deficiency causes beriberi; this vitamin does not depend on gastric factors for absorption.