Basophilic stippling is marked and target cells are common. The mean cell volume is commonly decreased (i.e., a microcytic anemia), but it may also be normal or even high. The RDW is increased with the red blood cell histogram shifted to the left. Leukocytes and platelets are normal. Bone marrow shows erythroid hyperplasia with a maturation arrest.In excess of 40% of the developing erythrocytes are ringed sideroblasts. Serum iron, percentage saturation and ferritin are increased. The total iron-binding capacity of the cells is normal to decreased. Stainable marrow hemosiderin is increased. Classification
Sideroblastic anemia is typically divided into subtypes based on its cause. Hereditary or congenital sideroblastic anemia may be X-linked or autosomal.GLRX5 has also been implicated. Acquired, or secondary, sideroblastic anemia develops after birth and is divided according to its cause. Laboratory findings
Serum Iron: high
increased ferritin levels
decreased total iron-binding capacity
high transferrin saturation
Hematocrit of about 20-30%
The mean corpuscular volume or MCV is usually normal or low for congenital causes of sideroblastic anemia but normal or high for acquired forms. With lead poisoning, see coarse basophilic stippling of red blood cells on peripheral blood smear
Specific test: Prussian blue stain of RBC in marrow shows ringed sideroblasts. Prussian blue staining involves a non-enzymatic reaction of ferrous iron with ferrocyanide forming ferric-ferrocyanide, which is blue in color. A counterstain may be used to provide better visualization. Treatment
Occasionally, the anemia is so severe that support with transfusion is required. These patients usually do not respond to erythropoietin therapy.
Trastuzumab deruxtecan, sold under the brand name Enhertu, is an antibody-drug conjugate consisting of the humanized monoclonal antibody trastuzumab (Herceptin) covalently linked to the topoisomerase I inhibitor deruxtecan (a derivative of exatecan). It is licensed for the treatment of breast cancer or gastric or gastroesophageal adenocarcinoma. Trastuzumab binds to and blocks signaling through epidermal growth factor receptor 2 (HER2/neu) on cancers that rely on it for growth. Additionally, once bound to HER2 receptors, the antibody is internalized by the cell, carrying the bound deruxtecan along with it, where it interferes with the cells ability to make DNA structural changes and replicate its DNA during cell division, leading to DNA damage when the cell attempts to replicate itself, destroying the cell.It was approved for medical use in the United States in December 2019, in Japan in March 2020, in the European Union in January 2021, and in Australia in October 2021.Trastuzumab deruxtecan is the first approved therapy by the US Food and Drug Administration (FDA) targeted to people with the HER2-low breast cancer subtype subset of HER2-negative breast cancer.