Hemolytic anemia is a condition that involves destruction of red blood cells (also called erythrocytes), faster than the bone marrow can normally produce. The medical term for red blood cell destruction is hemolysis. There are two types of hemolytic anemia:
- Intrinsic – the destruction of red blood cells is caused by a defect in the red blood cells. Among such diseases are sickle cell anemia and thalassemia, conditions characterized by the fact that red blood cells that do not survive as long as normal red blood cells. These diseases are often inherited.
- Extrinsic – red blood cells are healthy at the time of production but later are destroyed by infection, drugs, hypersplenism. There are other causes of extrinsic hemolytic anemia, also called immune hemolytic anemia, including:
- Infections -viral hepatitis, cytomegalovirus infection, Epstein-Barr virus (EBV) infection , typhoid fever, E. coli (Escherichia coli) and streptococci
- Drugs inclugind penicillin, malaria drugs, sulfa drugs or acetaminophen
- Leukemia or lymphoma
- Autoimmune disorders – systemic lupus erythematosus, rheumatoid arthritis, Wiskott-Aldrich syndrome or ulcerative colitis
- Various tumors.
Some types of extrinsic hemolytic anemia can be ameliorated only temporarily or for a few months. On the other hand some types of hemolytic anemia are chronic and include periods of remission and recurrence.
Hemolysis is triggered by a variety of hereditary or gained diseases. The etiology of premature destruction of red blood cells is diverse and may be caused by conditions such as intrinsic membrane defects, abnormal hemoglobin, erythrocyte enzyme defects, immune destruction of erythrocytes, damaged mechanics and hypersplenism. Hemolysis is associated with release of hemoglobin and lactic acid dehydrogenase. A patient with mild hemolysis may have normal hemoglobin levels if red blood cell production equelizes the rate of desctruction. Patients with mild hemolysis may experience anemia if bone marrow production of erythrocytes is low due to viral infections with parvovirus or other red blood cell destruction due to other infections. Deformities of the skull and skeleton may occur due to marked increase in hematopoiesis, bone expansion during childhood and early childhood diseases such as sickle cell anemia or thalassemia.
Causes and risk factors
Haemolysis causes include hereditary diseases with abnormal erythrocyte membrane and enzyme system or hemoglobin: hereditary spherocytosis, sickle cell anemia, immune conditions, toxic agents, antiviral agents, infections agents, mechanical injury. Therapy is different for each type of hemolytic anemia.
Hereditary diseases include:
- G-6-PD deficiency ( lack of an enzyme necessary in the red blood cell metabolism)
- Hereditary spherocytosis (smaller than normal red blood cells)
- Sickle cell anemia (red blood cells with the shape of a sickle)
Gained diseases include:
- Autoimmune hemolytic anemia can result from hot or cold agglutinin antibodies, most common warm antibodies are IgG and can be detected with direct Coombs test
- Autoimmune hemolytic anemia can occur after allogenic hematopoietic stem cell transplantation
- Microangiopathic anemia described in patients with disseminated intravascular coagulation, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura.
Sickle cell anemia
Is a severe inherited disease in which the body produces abnormal hemoglobin causing abnormal shaped erythrocytes. These abnormal red blood cells do not live as long as normal and they die after 10-20 days, while normal red cell die after 120.
Are inherited blood disease in which the body can not produce a certain type of hemoglobin.
This condition is characterized by a defect in the erythrocyte membrane surface that determines the shape of the sphere thus abnormal cells. They also present a shorter lifespan. This kind of disease is most common in people with European ancestry.
Deficiency of glucose-6-phosphate dehydrogenase (G-6-PD)
Erythrocytes with this condition lack an very important enzyme called G6PD . Cells that lack the enzyme are breaked by several triggering factors:, anti-malarials, exposure to naphthalene, fava beans, infections. The disease affects people African genetic heritage and the Mediterranean.
Autoimmune hemolytic anemia
The normal immune system can distinguish between its own and foreign structures. Thus it can attack any threat coming from the outside. In autoimmune hemolytic anemia the immune system produces antibodies that attack red blood cells, and no longer recognizes them as its own structures. The risk of autoimmunity occurs in lupus, chronic lymphocytic leukemia, non Hodgkin lymphoma, Epstein-Barr virus, cytomegalovirus infection, hepatitis, HIV. In some types of disease antibodies called cold agglutinins, destroys red blood cells at low temperatures of the environment and other hot agglutinins are active at high temperatures.
Posttransfusional hemolytic anemia
Occurs when the body produces antibodies against red blood cells that were transfused from another blood group.The condition occurs in pregnancy if there are differences between maternal and fetal blood type.