Aplastic anemia refers to anemia with pancytopenia associated with varying degrees of bone marrow hypoplasia/aplasia. The causes are diverse, and the condition has a very high mortality if left untreated. The loss of hematopoietic stem cells in aplastic anemia may be caused by direct toxic injury by drugs, chemicals, ionizing radiation, autoimmune processes, or infectious agents, as well as by clonal and genetic abnormalities. Bone marrow aspiration and biopsy is required to confirm the diagnosis and exclude other conditions that cause pancytopenia such as megaloblastic anemia and bone marrow infiltration.
If the incorporation of iron into the heme molecule is defective, hemoglobin synthesis is reduced; this condition is called sideroblastic anemia (SA). Diagnosis of SA is made primarily on the basis of bone marrow examination with Prussian blue stain. A normal sideroblast is an erythroblast with few granules of hemosiderin in the cytoplasm; but in SA, iron accumulation, particularly in the mitochondria, leads to development of the “ring sideroblast.” Sideroblastic anemia may be caused by a genetic disorder, or it may develop indirectly as part of a myelodysplastic syndrome (refractory anemia with ring sideroblasts) that can progress to acute myelogenous leukemia or other hematologic malignancies. Other causes of SA are usually acquired and include chronic alcoholism and lead poisoning.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.