Types of Hemolytic Anemia

There are many types of hemolytic anemia. Some types are inherited, which means a person is born with them. Other types are acquired, which means they develop in response to some other disease or factor.

Inherited Types of Hemolytic Anemia

In the inherited hemolytic anemias, one or more of the genes that control the production of red blood cells are defective, causing the bone marrow to make abnormal cells. The red blood cell abnormality can involve the cell membrane (the outer covering of the cell), the chemistry inside the cell, or the production of abnormal types or amounts of hemoglobin. The abnormal cells may be fragile and break down (hemolyze) on their own while circulating in the bloodstream. Also, the body's immune system may recognize that the red blood cells are abnormal, and an organ called the spleen may remove the cells from the bloodstream.

Sickle Cell Anemia

In sickle cell anemia, the body makes an abnormal type of hemoglobin. This hemoglobin causes the red blood cells to take on an abnormal shape. Instead of their normal shape (a doughnut without a hole) the red blood cells can turn into a sickle (crescent) shape. Sickle cells die and are removed from the bloodstream prematurely. In the United States, sickle cell anemia occurs most often in African Americans. There also are other types of abnormal hemoglobin that can cause hemolysis.

Thalassemia

The thalassemias are a group of anemias in which the body doesn't make enough of certain types of hemoglobin. This leads to abnormal red blood cells that die and are removed from the body prematurely. Thalassemia is most common among people of Mediterranean, African, or Southeast Asian descent.

Hereditary Spherocytosis

In hereditary spherocytosis (SFER-o-si-to-sis), an abnormality of the surface membrane of red blood cells causes them to take on a spherical (ball) shape. The abnormally shaped blood cells have a short lifespan. Hereditary spherocytosis is the most common cause of hemolytic anemia among people whose ancestors come from Northern Europe.

Hereditary Elliptocytosis (Ovalocytosis)

Hereditary elliptocytosis (e-LIP-to-si-TO-sis) is another condition involving the cell membrane. It's also known as hereditary ovalocytosis. In this condition, the red blood cells are elliptic (oval) in shape and not as flexible as normal red blood cells. These abnormal red blood cells also have a short lifespan.

Glucose-6-Phosphate Dehydrogenase Deficiency

In glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency), the red blood cells are missing an important enzyme called G6PD. G6PD is part of the normal chemistry inside red blood cells. In G6PD deficiency, if red blood cells come into contact with certain substances in the bloodstream, the missing enzyme causes the cells to rupture and die prematurely. The hemolysis can be triggered by the person taking sulfa or antimalaria medicines, eating fava beans, or having an infection. G6PD deficiency mostly affects males of African or Mediterranean descent. It affects about 1 in 10 African American males.

Pyruvate Kinase Deficiency

Pyruvate kinase also is an enzyme-deficiency hemolytic anemia in which the missing enzyme is called pyruvate kinase. Not having enough of this enzyme causes red blood cells to break down easily. This disorder is more common among the Amish than other groups.

Acquired Types of Hemolytic Anemia

In acquired types of hemolytic anemia, the red blood cells may be normal, but some other disease or factor causes the body to destroy the red blood cells and remove them from the bloodstream. The destruction of the red blood cells can occur in the bloodstream or, more commonly, in the spleen.

Immune Hemolytic Anemia

In immune hemolytic anemia, the body's immune system destroys the body's red blood cells. There are three main types of immune hemolytic anemia: autoimmune, alloimmune, and drug-induced.

Autoimmune hemolytic anemia. In autoimmune hemolytic anemia (AIHA), a person's immune system mistakenly produces antibodies directed against the person's own red blood cells. One-half of all cases of hemolytic anemia are AIHA. The cause of AIHA is unknown. It may come on very quickly and become serious. It's most common in people over age 40.

Having certain diseases or infections can make a person more likely to develop AIHA. These include chronic lymphocytic leukemia, non-Hodgkin's lymphoma, and other blood cancers; Epstein-Barr virus (which causes infectious mononucleosis); cytomegalovirus (a virus that infects cells); mycoplasma pneumonia (a lung infection); hepatitis; and human immunodeficiency virus (HIV).

In some types of AIHA, the antibodies produced by the body are called warm antibodies. This means they are active (that is, they destroy red blood cells) at warm temperatures, such as body temperature. In other types of AIHA, the body produces "cold-reactive antibodies," which means they become active when exposed to colder temperatures. Cold-reactive antibodies can become active when the body (typically the hands or feet) is exposed to temperatures of less than 32 to 50 degrees Fahrenheit (0 to 10 degrees Celsius). Warm antibody AIHA is more common than cold-reactive antibody AIHA.

Alloimmune hemolytic anemia. In alloimmune hemolytic anemia, antibodies are produced against the red blood cells a person receives in a blood transfusion. If the blood type used for the tranfusion is different than the recipient's blood type, the recipient's immune system can develop antibodies that attack and destroy the transfused blood cells.

Alloimmune antibodies also can develop as a result of the mixing of blood between a pregnant woman and her baby at delivery. If the mother's blood type is Rh-negative and the baby's is Rh-positive, the mother can produce antibodies against the baby's blood type. If a mother develops anti-Rh antibodies as a result of one pregnancy, they can cross the placenta during the next pregnancy and harm the fetus. To prevent this, a medicine called RhoGam can be given at the time of delivery to block the mother's body from developing antibodies against the baby's blood type.

Drug-induced hemolytic anemia. Certain drugs can cause a reaction that develops into hemolytic anemia. These drugs include high doses of penicillin and related drugs, acetaminophen, quinine and other drugs to treat malaria, anti-inflammatory drugs, and levodopa.

Mechanical Hemolytic Anemias

Physical damage to red blood cell membranes can result from microangiopathic (MI-kro-an-jee-o-PA-thik) changes in small blood vessels. An artificial heart valve or other device used in blood vessels also can damage red blood cell membranes. Damage can occur with a heart-lung bypass machine during open-heart surgery. Damage also can occur with preeclampsia or eclampsia (elevated blood pressure and protein in the urine after the 20th week of pregnancy). Blood cell damage may occur in the limbs while participating in marathons or other strenuous activities.

Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal (par-ok-SIZ-mal) nocturnal hemoglobinuria (PNH) is an acquired genetic disorder in which the red blood cells are abnormal due to a lack of certain proteins. The body destroys these cells more rapidly than normal. The destruction may occur continuously at a low level and flare up at times (paroxysmal). People with PNH are at increased risk for blood clots in the veins and low levels of white blood cells and platelets.

Other Causes of Damage to Red Blood Cells

Infections and other agents can invade and damage red blood cells. Malaria and "blackwater fever," tick-borne diseases, snake venom, and toxic chemicals can attack and destroy red blood cells, causing hemolytic anemia.