 For example, a person recently transfused for iron deficiency would have small, pale, iron deficient red blood cells (RBCs) and the donor RBCs of normal size and color.Similarly, a person transfused for severe folate or vitamin B12 deficiency would have two cell populations, but, in this case, the patient's RBCs would be larger and paler than the donor's RBCs.A person with sideroblastic anemia (a defect in heme synthesis, commonly caused by alcoholism, but also drugs/toxins, nutritional deficiencies, a few acquired and rare congenital diseases) can have a dimorphic smear from the sideroblastic anemia alone.