Hemolytic anemia: Part 1.

Abstract

1. Kwesi Sackey, MD* 1. 2. *Associate Professor, The University of Texas Medical Branch, Galveston, TX. After completing this article, readers should be able to: 1. Explain the role of immune reactions, red blood cell membrane defects, red blood cell enzyme defects, or hemoglobin abnormalities in the development of hemolytic anemia. 2. List the characteristic findings of hemolytic anemia. 3. Describe the significance of a low reticulocyte count in a patient who has chronic hemolysis. 4. Describe the potential complications of red blood cell transfusions. Hemolytic anemia arises from a shortened survival of red blood cells (RBCs) due to an inherent abnormality of the cell, environmental factors, or both. It can be characterized by varying degrees of anemia, jaundice, an enlarged spleen, or combinations of these conditions. If the hemolysis is massive, the urine may become dark due to hemoglobinuria. Findings on examination of the peripheral blood typically include changes in the morphology of the RBCs and an increase in reticulocyte count. A low reticulocyte count usually indicates poor production of RBCs. The major categories of hemolytic anemia are: 1) immune-mediated (alloimmune or autoimmune), 2) membrane defects (spherocytosis, elliptocytosis), 3) enzyme defects (glucose-6-phosphate dehydrogenase[ G6PD] deficiency, pyruvate kinase deficiency), and 4) hemoglobin defects (sickle cell disease, thalassemia). ### DEFINITION AND EPIDEMIOLOGY This hemolysis arises from a reaction between an individual’s RBCs and “naturally occurring antibodies” that usually are not present in that individual. The primary alloimmune types are Rh (anti-D) hemolytic disease in the newborn and ABO hemolytic disease. ABO hemolytic disease is several times more common than Rh hemolytic disease. ### PATHOGENESIS AND PATHOPHYSIOLOGY In Rh disease, the mother does not have the Rh antigen on her RBCs (ie, Rh-negative) and, therefore, develops antibodies to the Rh antigen in response to Rh-positive RBCs that leak into her circulatory system during late pregnancy or delivery. The antibodies (immunoglobulin G [IgG]) leak back from the mother into the fetal circulation during subsequent pregnancies, leading to hemolysis only in subsequent …