Which condition is most likely to yield a rightward shift in the RBC histogram?

Which condition is most likely to yield a rightward shift in the RBC histogram?

• A. Pernicious anemia
• B. Iron deficiency anemia
• C. Thalassemia
• D. Sideroblastic anemia

Answer: (A)

A rightward shift in the RBC histogram indicates macrocytosis—an increase in red cell size. Pernicious anemia, a vitamin B12 deficiency, impairs DNA synthesis, leading to megaloblastic erythropoiesis and enlarged red cells. This macrocytosis raises the mean cell size and shifts the histogram to the right. In contrast, iron deficiency anemia and thalassemia typically produce microcytosis (smaller cells) and shift the histogram left or show more variable shapes; sideroblastic anemia is usually microcytic or normocytic. So the condition most likely to yield a rightward shift is pernicious anemia.

A rightward shift in the RBC histogram indicates macrocytosis—an increase in red cell size. Pernicious anemia, a vitamin B12 deficiency, impairs DNA synthesis, leading to megaloblastic erythropoiesis and enlarged red cells. This macrocytosis raises the mean cell size and shifts the histogram to the right. In contrast, iron deficiency anemia and thalassemia typically produce microcytosis (smaller cells) and shift the histogram left or show more variable shapes; sideroblastic anemia is usually microcytic or normocytic. So the condition most likely to yield a rightward shift is pernicious anemia.