Which type of deficiency results in macrocytic anemia?

• A. Folic acid
• B. Vitamin C
• C. Vitamin K
• D. Vitamin A

Answer: (A)

Macrocytic anemia comes from impaired DNA synthesis in red blood cell precursors, causing the developing cells to become oversized (megaloblasts) and the circulating RBCs to have a larger than normal volume. Folic acid is essential for thymidine synthesis, a building block of DNA. Without enough folate, DNA replication in precursors slows or halts, cells grow larger but fail to divide properly, producing megaloblastic cells and macrocytosis. That’s why folic acid deficiency is the cause most consistent with macrocytic anemia. Deficiencies of vitamins C, K, or A lead to other problems (scurvy symptoms, bleeding/coagulation issues, and vision-related issues, respectively) and do not produce the characteristic macrocytosis.