B9 (folate) deficiency and B12 deficiency share which hematologic finding?

B9 (folate) deficiency and B12 deficiency share which hematologic finding?

• A. Megaloblastic anemia with macrocytosis
• B. Microcytic anemia
• C. Aplastic anemia
• D. Leukocytosis

Answer: (A)

Both folate and vitamin B12 are essential for DNA synthesis, particularly thymidine formation. When either deficiency occurs, developing blood cells in the bone marrow can’t synthesize DNA properly, so nuclear maturation lags behind cytoplasmic growth. That produces large, immature erythroid precursors called megaloblasts and leads to macrocytic (enlarged) red cells in the blood. The peripheral smear often shows increased mean corpuscular volume and hypersegmented neutrophils, reflecting the abnormal DNA replication. This combination—megaloblastic changes with macrocytosis—is the hallmark shared by folate and B12 deficiencies. Other patterns, like microcytic anemia, point to iron-related problems; aplastic anemia implies bone marrow failure from a different mechanism; leukocytosis isn’t characteristic of these deficiencies.

Both folate and vitamin B12 are essential for DNA synthesis, particularly thymidine formation. When either deficiency occurs, developing blood cells in the bone marrow can’t synthesize DNA properly, so nuclear maturation lags behind cytoplasmic growth. That produces large, immature erythroid precursors called megaloblasts and leads to macrocytic (enlarged) red cells in the blood. The peripheral smear often shows increased mean corpuscular volume and hypersegmented neutrophils, reflecting the abnormal DNA replication. This combination—megaloblastic changes with macrocytosis—is the hallmark shared by folate and B12 deficiencies. Other patterns, like microcytic anemia, point to iron-related problems; aplastic anemia implies bone marrow failure from a different mechanism; leukocytosis isn’t characteristic of these deficiencies.