Pernicious anemia is a macrocytic anemia characterized by which finding?

• A. Microcytosis
• B. Macrocytosis
• C. Normocytosis
• D. Anisocytosis

Answer: (B)

Pernicious anemia causes red blood cells to become larger than normal because vitamin B12 deficiency disrupts DNA synthesis in developing erythrocytes, leading to megaloblastic changes and an increased mean corpuscular volume. This enlargement is macrocytosis, the hallmark finding.

Microcytosis refers to small red cells (as in iron deficiency), normocytosis means normal-sized cells, and anisocytosis is variation in cell size—none of these describe the primary size change seen in pernicious anemia.