2020 Aug 16. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan–.
Sideroblastic anemia is a type of anemia that results from abnormal utilization of iron during erythropoiesis. There are different forms of sideroblastic anemia, and all forms are defined by the presence of ring sideroblasts in the bone marrow. Ring sideroblasts are erythroid precursors containing deposits of non-heme iron in mitochondria forming a ring-like distribution around the nucleus. The iron-formed ring covers at least one-third of the nucleus rim. Sideroblastic anemia is known to cause microcytic and macrocytic anemia depending on what type of mutation led to it. Unlike iron deficiency anemia, where there is depletion of iron stores, patients with sideroblastic anemia have normal to high iron levels. Other microcytic anemias include thalassemia and anemia of chronic disease.
The hemoglobin molecule contains an important protein called heme. Structurally, the heme contains four pyrrole rings joined by four methine bridges at the alpha position with an iron atom at the center of the ring. As a result of this protein molecule, the hemoglobin can perform its function of carrying oxygen to tissues. Other functions of the heme apart from the formation of hemoglobin include gas sensing, signal transduction, biological clock, circadian rhythm, and micro RNA processing.
Sideroblastic anemia is a result of abnormal erythropoiesis during heme production. 85% of heme is produced in the cytoplasm and mitochondria of the erythroblast cells while the remaining is produced in hepatocytes. In the Shemin pathway, eight different enzymes help to coordinate heme synthesis. These enzymes include aminolevulinic acid synthase ALAS, porphobilinogen synthase, porphobilinogen deaminase, uroporphyrinogen III synthase, uroporphyrinogen decarboxylase (UROD), coproporphyrinogen oxidase (CPOX), protoporphyrinogen oxidase (PPOX), and ferrochelatase (FECH). There are two forms of sideroblastic anemia-hereditary and acquired.
This review article will discuss the etiology, epidemiology, differential diagnosis, pathophysiology, treatment and management of sideroblastic anemia.