Aplastic Anemia

Definition

A variety of blood cells course through your bloodstream — red blood cells, white blood cells and platelets. All are important to your health. Red blood cells carry oxygen, white blood cells fight infection, and platelets help the blood to clot.
In aplastic anemia, your body stops producing enough new blood cells. This means you're fatigued and at higher risk of infections and uncontrolled bleeding.
A rare and serious condition, aplastic anemia can develop at any age. Treatment for aplastic anemia may include medications, blood transfusions or a bone marrow transplant. Once considered nearly always fatal, aplastic anemia has a much better prognosis today, thanks to advances in treatment.

Symptoms

Aplastic anemia symptoms result from a shortage of one or more types of blood cells. Signs and symptoms may include:

Fatigue
Shortness of breath with exertion
Rapid heart rate
Pale skin
Frequent or prolonged infections
Unexplained or easy bruising  
Nosebleeds and bleeding gums
Prolonged bleeding from cuts
Skin rash
Dizziness
Headache
Aplastic anemia can come on suddenly or develop slowly over weeks or months. The illness may be brief, or it may become chronic. Without treatment, it may progress and become fatal.

Causes

Within the cavity of many of your bones, such as your pelvic bones, is a red, spongy material called bone marrow.

Bone marrow has a critical function. It contains special cells called stem cells, which are precursors of other cells. Stem cells in the bone marrow produce blood cells — red cells, white cells and platelets — that eventually leave the bone marrow and enter your bloodstream. Stem cells also make more stem cells.

Your bone marrow needs to continually produce new blood cells of all types to replace old ones. Red blood cells live about 120 days, platelets about seven days and most white blood cells a day or less before they're used and absorbed by your body.

Damage to bone marrow
Normally, your bone marrow supplies the right numbers of blood cells to keep you healthy. Aplastic anemia develops when damage occurs to your bone marrow, slowing or shutting down the production of new blood cells — a serious problem. Factors that can temporarily or permanently injure bone marrow include:

High-dose radiation and chemotherapy treatments. While these cancer-fighting therapies kill cancer cells, they can also damage healthy cells, including stem cells in bone marrow. Secondary aplastic anemia can be a temporary side effect of these treatments.
Exposure to toxic chemicals. Exposure to toxic chemicals, such as some used in pesticides and insecticides, may cause secondary aplastic anemia. Exposure to benzene — an ingredient in gasoline — also has been linked to secondary aplastic anemia. This type of anemia sometimes gets better on its own if you avoid repeated exposure to the chemicals that caused your initial illness.
Use of certain drugs. Some medications, such as those used to treat rheumatoid arthritis and some antibiotics, can cause secondary aplastic anemia.
Autoimmune disorders. An autoimmune disorder, such as lupus, in which your immune system begins attacking healthy cells, may involve stem cells in your bone marrow.
A viral infection. Viral infections that affect bone marrow may play a role in the development of aplastic anemia in some people.
Pregnancy. Aplastic anemia that occurs in pregnancy may be related to an autoimmune problem — your immune system begins attacking your bone marrow during pregnancy.
Unknown factors. In about half of cases, doctors aren't able to identify the cause of aplastic anemia. This is called idiopathic aplastic anemia.
In aplastic anemia, the bone marrow is described in medical terms as aplastic or hypoplastic — meaning that it's empty, or contains very few blood cells.

Confusion with myelodysplastic syndrome
Aplastic anemia can be mistaken for a condition called myelodysplastic syndrome. In this group of disorders, the bone marrow produces new blood cells, but they're deformed and underdeveloped. The bone marrow in myelodysplastic syndrome is sometimes called hyperplastic — meaning that it's packed with blood cells. But some people with myelodysplastic syndrome have empty marrow that's difficult to distinguish from aplastic anemia.

Because myelodysplastic syndrome also results in a shortage of healthy blood cells, it causes signs and symptoms similar to those of aplastic anemia — fatigue, unexplained bruising and easy bleeding. Doctors distinguish myelodysplastic syndrome from aplastic anemia using a bone marrow biopsy and genetic analysis of the bone marrow. Myelodysplastic syndrome — which is more common in older people — is also serious and treated with some of the same therapies as those used to treat aplastic anemia.
Risk factors
Aplastic anemia is rare. Factors that can increase your risk include:

Treatment with high-dose radiation or chemotherapy for cancer
Exposure to toxic chemicals
Use of prescription drugs — such as chloramphenicol (Chloromycetin) used to treat bacterial infections and gold compounds used to treat rheumatoid arthritis — that are known to rarely induce aplastic anemia
Use of inhalants — such as paint thinner, gasoline, nail polish remover, glues and lighter fluid
Certain blood diseases, autoimmune disorders and serious infections
Pregnancy, rarely
Tests and diagnosis
Doctors diagnose aplastic anemia using blood tests and bone marrow biopsy.

Blood tests. Normally, red blood cell, white blood cell and platelet levels stay within a certain range. Your doctor may suspect aplastic anemia when all three of these blood cell levels are very low. Many conditions can cause low blood cell counts, but usually of just one type of blood cell. For example, other types of anemia cause a decrease in red blood cells. If you have an infection, your white blood cell count alone may be low.
Bone marrow biopsy. To confirm a diagnosis, you'll need to undergo a bone marrow biopsy. In this procedure, a doctor uses a needle to remove a small sample of bone marrow from a large bone in your body, such as your hipbone. The bone marrow sample is examined under a microscope to rule out other blood-related diseases. In aplastic anemia, bone marrow contains fewer blood cells than normal. The few cells that are present, however, are normal. In diseases such as leukemia and myelodysplastic syndrome, the bone marrow is full of abnormal blood cells.
Prevention
There's no prevention for most cases of aplastic anemia. However, avoiding exposure to insecticides, herbicides, organic solvents, paint removers and other toxic chemicals may lower your risk of the disease. This is especially important if you've already had aplastic anemia that was caused by toxic chemicals. Exposure to the same compound a second time may cause the condition to return.