Overview of Hemolytic Anemias

Hemolytic anemia is a type of anemia that is characterized by progressive destruction of red blood cells or erythrocytes.  The cause to this destruction can be either genetic or acquired.  Three genetic diseases that cause hemolytic anemia will be discussed here.  These are: sickle cell anemia and thalassemia in addition to G6PD deficiency anemia.

The acquired type of hemolytic anemia can be caused due to a trauma.  In addition, it can occur due to a biochemical or physical agent that can destroy the red blood cells.  Red blood cells do not have nuclei.  Therefore it does not have the machinary to synthesize its own proteins because it does not have DNA. 

The life cycle of a normal red blood cell is approximately 120 days.  Accelerated death of red blood cells is called hemolytic anemia.  The damage to red blood cells can be either in the blood vessels or outside it.  Destruction of red blood cells inside the blood vessels is called intravascular destruction.  While that which occurs outside the vessels is called extravascular. 

Destruction of red blood cells due to a trauma or physical agent is termed intravascular hemolytic anemia.  On the other hand, red blood cells that are destroyed by white blood cells through phagocytosis is called extravascular hemolytic anemia.   The characteristics of this type of anemia are: increased rate of red blood cells destruction in addition to compensatory erythropoiesis or synthesis of red blood cells.       

The products of red blood cells destruction include iron metal in addition to hemoglobin and hemosiderin.  The result of hemolysis include hemoglobinemia or increased level of hemoglobin in the blood.  In addition, there is hemoglobinurea or the presence of hemoglobin in the urine of affected individuals. 

Hemosiderinurea or the presence of hemosiderin in the urine is also observed.  In addition the degradation of hemoglobin molecules into its constituents amino acids and heme molecules lead to the accumulation of the pigment bilirubin which is the biochemical degradation product of the heme molecule of the hemoglobin entity. 

Thus one of the symptoms of hemolytic anemia is jaundice or yellowing of the skin color of affected individuals.  This is so due to the accumulation of bilirubin in the blood which is a yellow pigment that imparts the skin a yellow color. 

Intravascular hemolysis of red blood cells can sometimes cause acute tubular necrosis with subsequent renal failure.  White blood cells on the other hand are the usual site of red blood cells destruction.  Red blood cells are usually biconcave in structure.  Its cellular membrane is flexible and easily deformable. 

In sickle cell anemia the beta-globin chain is altered in structure due to a genetic cause.  Thus the structure of the cell membrane is changed and adopts a sickled shape.  This structure is not easily deformable and thus is easily destroyed by white blood cells. 

In thalassemia the disorder is in the hemoglobin molecule is in the alpha or beta globin chain.  There is a reduced amount of healthy globin chains.  Thus the hemoglobin molecule synthesis is impaired  and thus the overall picture is is impairment of erythropoisis or synthesis of red blood cells.  Hemolysis in thalassemia can occur easily due to the altered structure of the hemoglobin molecule. 

Glucose-6-Phsphate dehydrogenase deficiency anemia or G6PD anemia causes another type of hemolytic anemia.  This enzyme usually protects the cell from oxidant effects by catalyzing the reduction of glutathione to its reduce form.  Its deficiency leads to damage to the cell membrane by existing oxidants.  Thus causing hemolysis.