What type of anemia is characterized by both microcytic and macrocytic features on a blood smear due to defective hemoglobin synthesis?

Sideroblastic anemia is characterized by the presence of both microcytic and macrocytic red blood cells on a blood smear due to an impairment in hemoglobin synthesis. In this condition, the bone marrow produces ringed sideroblasts instead of healthy, mature red blood cells. The defective synthesis of hemoglobin leads to ineffective erythropoiesis, where the cells cannot adequately incorporate iron into hemoglobin, resulting in a dual population of red blood cells—some appear microcytic (small) due to a lack of hemoglobin, while others may become macrocytic (large) as a consequence of the increased mean corpuscular volume from ineffective erythropoiesis.

In contrast, iron deficiency anemia primarily presents with microcytic red blood cells and does not typically show macrocytic features because it lacks the disrupted hemoglobin synthesis seen in sideroblastic anemia. Thalassemia also leads to microcytic anemia due to defects in globin chain production but, similar to iron deficiency, does not exhibit macrocytic characteristics. Lastly, vitamin B12 deficiency leads to macrocytic anemia due to impaired DNA synthesis but does not result in microcytic cells as seen in sideroblastic anemia. Thus, the unique combination of