What Is Aplastic Anemia?

Aplastic anemia (a-PLAS-tik uh-NEE-me-uh) is a rare and serious blood disorder in which bone marrow stops making enough new blood cells. Bone marrow––the spongy material inside bones—makes new blood cells called stem cells. Stem cells normally develop into three main types of blood cells: red blood cells, white blood cells, and platelets. Each type of blood cell has its own functions in the body.

It is normal for blood cells to die. The lifespan of red blood cells is about 120 days. White blood cells live less than 1 day. Platelets live about 6 days. As a result, bone marrow must constantly make new blood cells. The term "anemia" is most often used to mean a condition in which a person’s number of red blood cells is too low or their red blood cells do not carry enough hemoglobin (HEE-muh-glow-bin). However, in aplastic anemia, normal production of all blood cells—red cells, white cells, and platelets—slows or stops. This is because the stem cells have been damaged. The cause of this damage is often unknown.

Effects of Aplastic Anemia on the Body

A shortage of any one of the three main types of blood cells will have an effect on the body. In aplastic anemia, however, the body must cope with a shortage of all three types of blood cells. Severe aplastic anemia that is not treated promptly can be fatal.

The effect on the body of a shortage of each type of blood cell is described below:

• Too few red blood cells. Red blood cells contain hemoglobin, which is an iron-rich protein that gives blood its red color. Hemoglobin carries oxygen from the lungs to the rest of the body. Red blood cells also remove carbon dioxide (a waste product) from cells and carry it to the lungs to be exhaled. If there are not enough red blood cells, too little oxygen is carried to the body and too little carbon dioxide is carried away. People who have a low red blood cell count often feel tired because the body is not getting enough oxygen. An untreated or severely low red blood cell count can lead to many problems. The heart has to work harder to pump blood to get enough oxygen to the body’s organs and tissues. Over time, this stress on the heart can cause fast or irregular heartbeats, an enlarged heart, or even heart failure.
• Too few white blood cells. White blood cells fight infection and are an important part of the body’s defense system. When the number of white blood cells in the blood is lower than normal, the body is less able to fight infections. A person may become ill more often, and the illness may be very severe or last a long time.
• Too few platelets. Platelets are needed to help blood clot. If the platelet count is low, blood cannot clot normally. A person with a low platelet count may bruise or bleed easily, and the bleeding may be hard to stop.

Important General Information

Aplastic anemia is a rare condition. In the United States, about 500–1,000 people develop this type of anemia each year. It is two to three times more common in Asian countries.

The two main types of aplastic anemia are acquired and hereditary. Acquired means a person develops the condition during his or her lifetime. Hereditary means a person is born with the condition. Acquired aplastic anemia is the most common type, and it is sometimes a temporary condition. It can be triggered by exposure to:

• Toxic chemicals
• Chemotherapy drugs
• Radiation
• Virus infections

However, the cause of acquired aplastic anemia is often not known.

Hereditary aplastic anemia is rare. It occurs with some inherited conditions, such as Fanconi anemia.

Severity of Aplastic Anemia

Aplastic anemia can begin suddenly or develop slowly. It tends to get worse over time, except when a cause can be found and removed. Its severity ranges from mild to very severe.

• People with mild or moderate aplastic anemia have low blood counts that the doctor will check often. If the blood counts do not get worse, treatment may not be needed.
• People with severe aplastic anemia have very low blood counts. The condition can become life threatening if it is not treated.
• People with very severe aplastic anemia have extremely low blood counts. This condition is life threatening. It needs emergency hospital treatment.

Although aplastic anemia is not cancer, the treatments for it are similar to those used for some types of cancer. Treatments include blood transfusions and bone marrow transplants. Treatments also include medicines to suppress the immune system, stimulate the bone marrow, and treat infections.

Outlook

Many people with aplastic anemia can be treated successfully if they have prompt and appropriate treatment. Some people with aplastic anemia can be cured with a bone marrow transplant.

December 2007