Which vitamin deficiency commonly presents with neuropathy and anemia and is treated with supplementation?

• A. Vitamin C deficiency
• B. Vitamin B12 deficiency
• C. Vitamin D deficiency
• D. Vitamin K deficiency

Answer: (B)

Deficiency of vitamin B12 causes both neurologic damage and macrocytic anemia. The neurologic signs come from impaired myelin formation, leading to demyelination of the posterior columns and lateral corticospinal tracts. This produces numbness or tingling, proprioceptive loss, gait instability, and sometimes a positive Romberg. At the same time, B12 is essential for DNA synthesis in rapidly dividing cells, so its absence leads to macrocytic (megaloblastic) anemia with impaired red cell production. Because the underlying issue is lack of B12, the treatment is to replenish the vitamin, typically with cyanocobalamin or hydroxocobalamin. In cases of pernicious anemia or malabsorption, parenteral B12 is commonly required, while some patients may tolerate high-dose oral B12 if absorption is sufficient. The other vitamins don’t classically cause this combination of neuropathy plus macrocytic anemia: deficiencies like vitamin C cause bleeding tendencies and other symptoms; vitamin D deficiency affects bones and muscles; vitamin K deficiency leads to bleeding due to impaired clotting factors.