Aplastic anemia

Synonyms

4

Overview

Aplastic anemia is failure of the bone marrow to produce enough blood cells- it's empty (aplastic) or contains very few blood cells (hypoplastic). All blood cell types are affected in this condition: red blood cells (anemia), white blood cells (leukopenia), and platelets (thrombocytopenia). Aplastic refers to inability of the stem cells to generate mature blood cells. It can be caused by injury to blood stem cells due to exposure to certain drugs, chemotherapy, congenital disorders, drug therapy to suppress the immune system, pregnancy, radiation therapy, or toxins such as benzene or arsenic. When the cause is unknown, it is referred to as idiopathic aplastic anemia. In about half of all cases, no cause can be found. The condition can be acute or chronic.

Symptoms

Aplastic anemia symptoms may include:

• Fatigue
• Shortness of breath with exertion
• Rapid or irregular 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 progress slowly over weeks or months, or it may come on suddenly. The illness may be brief, or it may become chronic. Aplastic anemia can be very severe and even fatal.

Causes

Factors that can temporarily or permanently injure bone marrow and affect blood cell production include:

• Radiation and chemotherapy treatments. While these cancer-fighting therapies kill cancer cells, they can also damage healthy cells, including stem cells in bone marrow. 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 aplastic anemia. Exposure to benzene — an ingredient in gasoline — also has been linked to aplastic anemia. This type of anemia may get 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 aplastic anemia.
• Autoimmune disorders. An autoimmune disorder, 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. Viruses that have been linked to the development of aplastic anemia include hepatitis, Epstein-Barr, cytomegalovirus, parvovirus B19 and HIV.
• Pregnancy. Aplastic anemia that occurs in pregnancy may be related to an autoimmune problem — your immune system may attack your bone marrow during pregnancy.
• Unknown factors. In many cases, doctors aren't able to identify the cause of aplastic anemia. This is called idiopathic aplastic anemia.

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.

Some people with aplastic anemia also have a rare disorder known as paroxysmal nocturnal hemoglobinuria. This disorder causes red blood cells to break down too soon. Paroxysmal nocturnal hemoglobinuria can lead to aplastic anemia, or aplastic anemia can evolve into paroxysmal nocturnal hemoglobinuria.

Fanconi's anemia is a rare, inherited disease that leads to aplastic anemia. Children born with it tend to be smaller than average and have birth defects, such as underdeveloped limbs. The disease is diagnosed with the help of blood tests.

Prevention

Aplastic anemia is rare and there is no prevention for most cases  however avoiding exposure may lower your risk of the disease.
Factors that may increase your risk include:

• Treatment with high-dose radiation or chemotherapy for cancer
• Exposure to toxic chemicals such as insecticides, herbicides, organic solvents, paint removers and other toxic chemicals 
• The use of some prescription drugs — such as chloramphenicol, which is used to treat bacterial infections, and gold compounds used to treat rheumatoid arthritis
• Certain blood diseases, autoimmune disorders and serious infections
• Pregnancy, rarely

Diagnosis

To diagnose aplastic anemia, your doctor may recommend:

• 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.
• 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.

Once you've received a diagnosis of aplastic anemia, you may need additional tests to determine an underlying cause.

Prognosis

Acquired aplastic anemia usually gets worse unless the cause is removed or the disease is treated. Mild and moderate forms of the disease often progress slower than the severe form. Bone marrow transplant has been successful in young patients with a long-term survival rate of approximately 80%. Older patients have a survival rate of 40 - 70% after a transplant. If left untreated, severe aplastic anemia can become life threatening.

Treatment

Treatments for aplastic anemia may include observation for mild cases, blood transfusions and medications for more-serious cases, and in severe cases, bone marrow transplantation. Severe aplastic anemia, in which your blood cell counts are extremely low, is life-threatening and requires immediate hospitalization for treatment.

Treatment for aplastic anemia usually involves blood transfusions to control bleeding and relieve anemia symptoms. Blood transfusions aren't a cure for aplastic anemia. But they do relieve signs and symptoms by providing blood cells that your bone marrow isn't producing. A transfusion may include:

• Red blood cells. Transfusions of red blood cells raise red blood cell counts. This helps relieve anemia and fatigue.
• Platelets. Transfusions of platelets help prevent excessive bleeding.

While there's generally no limit to the number of blood cell transfusions you can have, complications can sometimes arise with multiple transfusions. Transfused red blood cells contain iron that can accumulate in your body and can damage vital organs if an iron overload isn't treated. Medications can help your body get rid of excess iron. Another possible complication is that over time, your body may develop antibodies to transfused blood cells, making them less effective at relieving symptoms. However, the use of immunosuppressant medication makes this complication less likely.

Stem cell transplant
A stem cell transplant to rebuild the bone marrow with stem cells from a donor may offer the only successful treatment option for people with severe aplastic anemia. A stem cell transplant, which is also called a bone marrow transplant, is generally the treatment of choice for people who are younger and have a matching donor — most often a sibling.
If a donor is found, your diseased bone marrow is first depleted with radiation or chemotherapy. Healthy stem cells from the donor are filtered from the blood. The healthy stem cells are injected intravenously into your bloodstream, where they migrate to the bone marrow cavities and begin generating new blood cells. The procedure requires a lengthy hospital stay. After the transplant, you'll receive drugs to help prevent rejection of the donated stem cells.
A stem cell transplant carries risks. There's a chance that your body may reject the transplant, leading to life-threatening complications. In addition, not everyone is a candidate for transplantation or can find a suitable donor.

Immunosuppressants
For people who can't undergo a bone marrow transplant or for those whose aplastic anemia may be due to an autoimmune disorder, treatment may involve drugs that alter or suppress the immune system (immunosuppressants).

Drugs such as cyclosporine (Gengraf, Neoral, Sandimmune) and anti-thymocyte globulin (Thymoglobulin) are examples. These drugs suppress the activity of immune cells that are damaging your bone marrow. This helps your bone marrow recover and generate new blood cells. Cyclosporine and anti-thymocyte globulin are often used in combination.

Corticosteroids, such as methylprednisolone (Medrol, Solu-Medrol), are often given at the same time as these drugs.

Immune-suppressing drugs can be very effective at treating aplastic anemia. The downside is that these drugs further weaken your immune system. It's also possible that after you stop taking these drugs, aplastic anemia may return.

Bone-marrow stimulants
Certain drugs — including colony-stimulating factors, such as sargramostim (Leukine), filgrastim (Neupogen) and pegfilgrastim (Neulasta), and epoetin alfa (Epogen, Procrit) — may help stimulate the bone marrow to produce new blood cells. Growth factors are often used in combination with immune-suppressing drugs.

Antibiotics, antivirals
Having aplastic anemia weakens your immune system. You have fewer white blood cells in circulation to fight off germs. This leaves you susceptible to infections.

At the first sign of infection, such as a fever, see your doctor. You don't want the infection to get worse, because it could prove life-threatening. If you have severe aplastic anemia, your doctor may give you antibiotics or antiviral medications to help prevent infections.

Other treatments
Aplastic anemia caused by radiation and chemotherapy treatments for cancer usually improves once you complete those treatments. The same is true for most other drugs that induce aplastic anemia.

Pregnant women with aplastic anemia are treated with blood transfusions. For many women, pregnancy-related aplastic anemia improves once the pregnancy ends. If that doesn't happen, treatment is still necessary.

Resources

• NIH