Aplastic Anemia overview
Aplastic anemia is a condition that occurs when your body stops producing enough new blood cells. Aplastic anemia leaves you feeling fatigued and with a higher risk of infections and uncontrolled bleeding. A rare and serious condition, aplastic anemia can develop at any age. Aplastic anemia may occur suddenly, or it can occur slowly and get worse over a long period of time. Treatment for aplastic anemia may include medications, blood transfusions or a stem cell transplant, also known as a bone marrow transplant.
Aplastic anemia is a rare disease in which the bone marrow and the hematopoietic stem cells that reside there are damaged. This causes a deficiency of all three blood cell types (pancytopenia): 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 is more frequent in people in their teens and twenties, but is also common among the elderly. It can be caused by heredity, immune disease, or exposure to chemicals, drugs, or radiation. However, in about half the cases, the cause is unknown.
The definitive diagnosis is by bone marrow biopsy; normal bone marrow has 30–70% blood stem cells, but in aplastic anemia, these cells are mostly gone and replaced by fat. First line treatment for aplastic anemia consists of immunosuppressive drugs, typically either anti-lymphocyte globulin or anti-thymocyte globulin, combined with corticosteroids and ciclosporin. Hematopoietic stem cell transplantation is also used, especially for patients under 30 years of age with a related matched marrow donor.
Aplastic anemia is a type of anemia. The term “anemia” usually refers to a condition in which your blood has a lower than normal number of red blood cells. Anemia also can occur if your red blood cells don’t contain enough hemoglobin (HEE-muh-glow-bin). This iron-rich protein helps carry oxygen to your body.
In people who have aplastic anemia, the body doesn’t make enough red blood cells, white blood cells, and platelets. This is because the bone marrow’s stem cells are damaged. (Aplastic anemia also is called bone marrow failure.) Many diseases, conditions, and factors can damage the stem cells. These conditions can be acquired or inherited. “Acquired” means you aren’t born with the condition, but you develop it. “Inherited” means your parents passed the gene for the condition on to you.
In many people who have aplastic anemia, the cause is unknown.
- Aplastic anemia symptoms may include:
- 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
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.
Anemia may lead to malaise, pallor and associated symptoms such as palpitations.
Low platelet counts (thrombocytopenia) if present is associated with an increased risk of hemorrhage, bruising and petechiae. Low white blood cell counts (leukocytopenia) if present leads to an increased risk of infections which can be severe. Aplastic anemia is a rare but serious blood disorder. If you have it, your bone marrow doesn’t make enough new blood cells. There are different types, including Fanconi anemia. Causes include.
- Toxic substances, such as pesticides, arsenic, and benzene
- Radiation therapy and chemotherapy for cancer
- Certain medicines
- Infections such as hepatitis, Epstein-Barr virus, or HIV
- Autoimmune disorders
- Certain inherited conditions
In many people, the cause is unknown.
Symptoms include fatigue, weakness, dizziness, and shortness of breath. It can cause heart problems such as an irregular heartbeat, an enlarged heart, and heart failure. You may also have frequent infections and bleeding.
Your doctor will diagnose aplastic anemia based on your medical and family histories, a physical exam, and test results. Once your doctor knows the cause and severity of the condition, he or she can create a treatment plan for you. Treatments include blood transfusions, blood and marrow stem cell transplants, and medicines. The symptoms of AA are not caused by damage to stem cells but by the lack of normal blood cells. The most common symptoms are those of anaemia or of bleeding due to low platelet counts but infection may also be a symptom at diagnosis, especially if the neutrophil count is very low.
- Anaemia due to lack of red blood cells – weakness, tiredness, shortness of breath, light-headedness, palpitations.
- Bleeding and bruising due to lack of platelets – purpura (small bruises in the skin), nosebleeds, bleeding gums, vision problems (bleeding in the retina). Severe bleeding is not common but requires urgent treatment.
- Infections due to lack of white blood cells – infection may be a significant problem at the time of diagnosis. Severe infection requires urgent treatment.
Aplastic anemia symptoms vary from person to person. Specific symptoms depend on which of your blood cell types are affected and how low your blood counts have fallen.
Each type of blood cell has a different role:
- Red cells carry oxygen around the body.
- White cells fight infections.
- Platelets prevent bleeding.
Your symptoms depend on what type of blood cells you’re low on, but you may be low on all three. These are common symptoms for each:
Low red blood cell count:
- Shortness of breath
- Pale skin
- Chest pain
- Irregular heartbeat
Low white blood cell count:
Low platelet count:
- Easy bruising and bleeding
If you have some of these symptoms, your doctor may do a test called a complete blood count. She may also take a biopsy of your bone marrow to check you for this disorder.
Aplastic anemia develops when damage occurs to your bone marrow, slowing or shutting down the production of new blood cells. Bone marrow is a red, spongy material inside your bones that produces stem cells, which give rise to other cells. Stem cells in the bone marrow produce blood cells — red cells, white cells and platelets. In aplastic anemia, the bone marrow is described in medical terms as aplastic or hypoplastic — meaning that it’s empty (aplastic) or contains very few blood cells (hypoplastic).
Aplastic anemia can be caused by exposure to certain chemicals, drugs, radiation, infection, immune disease; in about half the cases, a definitive cause is unknown. It is not a familial line hereditary condition, nor is it contagious. It can be acquired due to exposure to other conditions but if a person develops the condition, their offspring would not develop it by virtue of their gene connection.
Aplastic anemia is also sometimes associated with exposure to toxins such as benzene, or with the use of certain drugs, including chloramphenicol, carbamazepine, felbamate, phenytoin, quinine, and phenylbutazone. Many drugs are associated with aplasia mainly according to case reports, but at a very low probability. As an example, chloramphenicol treatment is followed by aplasia in less than one in 40,000 treatment courses, and carbamazepine aplasia is even rarer.
Exposure to ionizing radiation from radioactive materials or radiation-producing devices is also associated with the development of aplastic anemia. Marie Curie, famous for her pioneering work in the field of radioactivity, died of aplastic anemia after working unprotected with radioactive materials for a long period of time; the damaging effects of ionizing radiation were not then known.
Aplastic anemia is present in up to 2% of patients with acute viral hepatitis.
One known cause is an autoimmune disorder in which white blood cells attack the bone marrow.
Short-lived aplastic anemia can also be a result of parvovirus infection. In humans, the P antigen (also known as globoside), one of the many cellular receptors that contribute to a person’s blood type, is the cellular receptor for parvovirus B19 virus that causes erythema infectiosum (fifth disease) in children. Because it infects red blood cells as a result of the affinity for the P antigen, Parvovirus causes complete cessation of red blood cell production. In most cases, this goes unnoticed, as red blood cells live on average 120 days, and the drop in production does not significantly affect the total number of circulating red blood cells. In people with conditions where the cells die early (such as sickle cell disease), however, parvovirus infection can lead to severe anemia.
More frequently parvovirus B19 is associated with aplastic crisis which involves only the red blood cells ( despite the name). Aplastic anemia involves all different cell lines.
In some animals, aplastic anemia may have other causes. For example, in the ferret (Mustela putorius furo), it is caused by estrogen toxicity, because female ferrets are induced ovulators, so mating is required to bring the female out of heat. Intact females, if not mated, will remain in heat, and after some time the high levels of estrogen will cause the bone marrow to stop producing red blood cells
It is generally accepted that, in most cases, acquired AA is caused by the body’s immune system damaging stem cells in the bone marrow. When the immune system attacked the body’s own cells, this is called an autoimmune disease. In about three-quarters of all cases there is obvious underlying reason why the immune system is damaging stem cells. This is called idiopathic aplastic anaemia.
In the remaining quarter, there may have been recent exposure which is thought to have triggered the development of AA:
- Medicine – one example of a medicine that may cause AA is the antibiotic chloramphenicol, when given orally or by injection. This drug is only used for life-threatening infections which are resistant to other antibiotics.
- Chemical – one example is the exposure to high levels of benzene. In the UK, this probably accounts for very few cases, as there are strict limits on exposure to this sort of chemical.
- Viral infection – about 1 in 10 patients with AA have had a recent viral infection, often hepatitis. In these cases, the AA may develop because the patient’s stem cells have some surface proteins which are similar to those on the virus. The immune system becomes ‘confused’ and produces antibodies which are targeted at the virus but also damage blood-forming stem cells.
Aplastic anemia occurs when blood-forming stem cells in bone marrow can’t produce enough red blood cells, white blood cells or platelets. The cells that are made are normal. Sometimes there’s a genetic cause that was passed from parent to child, but most often it results from the accidental destruction of stem cells by the immune system. Damage to the bone marrow’s stem cells causes aplastic anemia. When stem cells are damaged, they don’t grow into healthy blood cells.
The cause of the damage can be acquired or inherited. “Acquired” means you aren’t born with the condition, but you develop it. “Inherited” means your parents passed the gene for the condition on to you. Acquired aplastic anemia is more common, and sometimes it’s only temporary. Inherited aplastic anemia is rare.
In many people who have aplastic anemia, the cause is unknown. Some research suggests that stem cell damage may occur because the body’s immune system attacks its own cells by mistake.
The condition needs to be differentiated from pure red cell aplasia. In aplastic anemia, the patient has pancytopenia (i.e., leukopenia and thrombocytopenia) resulting in decrease of all formed elements. In contrast, pure red cell aplasia is characterized by reduction in red cells only. The diagnosis can only be confirmed on bone marrow examination. Before this procedure is undertaken, a patient will generally have had other blood tests to find diagnostic clues, including a complete blood count, renal function and electrolytes, liver enzymes, thyroid function tests, vitamin B12 and folic acid levels.
The following tests aid in determining differential diagnosis for aplastic anemia:
- Bone marrow aspirate and biospy: to rule out other causes of pancytopenia (i.e. neoplastic infiltration or significant myelofibrosis).
- History of iatrogenic exposure to cytotoxic chemotherapy: can cause transient bone marrow suppression
- X-rays, computed tomography (CT) scans, or ultrasound imaging tests: enlarged lymph nodes (sign of lymphoma), kidneys and bones in arms and hands (abnormal in Fanconi anemia)
- Chest X-ray: infections
- Liver tests: liver diseases
- Viral studies: viral infections
- Vitamin B12 and folate levels: vitamin deficiency
- Blood tests for paroxysmal nocturnal hemoglobinuria
- Test for antibodies: immune competency
Many tests and tools are used to diagnose aplastic anemia. These help to confirm the diagnosis, look for its cause and find out how severe it is. They are also used to rule out other conditions that may cause similar symptoms.
Treating immune-mediated aplastic anemia involves suppression of the immune system, an effect achieved by daily medicine intake, or, in more severe cases, a bone marrow transplant, a potential cure. The transplanted bone marrow replaces the failing bone marrow cells with new ones from a matching donor. The multipotent stem cells in the bone marrow reconstitute all three blood cell lines, giving the patient a new immune system, red blood cells, and platelets. However, besides the risk of graft failure, there is also a risk that the newly created white blood cells may attack the rest of the body (“graft-versus-host disease”). In young patients with an HLA matched sibling donor, bone marrow transplant can be considered as first-line treatment, patients lacking a matched sibling donor typically pursue immunosuppression as a first-line treatment, and matched unrelated donor transplants are considered a second-line therapy.
Medical therapy of aplastic anemia often includes a course of antithymocyte globulin (ATG) and several months of treatment with ciclosporin to modulate the immune system. Chemotherapy with agents such as cyclophosphamide may also be effective but has more toxicity than ATG. Antibody therapy, such as ATG, targets T-cells, which are believed to attack the bone marrow. Corticosteroids are generally ineffective, though they are used to ameliorate serum sickness caused by ATG. Normally, success is judged by bone marrow biopsy 6 months after initial treatment with ATG.
One prospective study involving cyclophosphamide was terminated early due to a high incidence of mortality, due to severe infections as a result of prolonged neutropenia.
In the past, before the above treatments became available, patients with low leukocyte counts were often confined to a sterile room or bubble (to reduce risk of infections), as in the case of Ted DeVita.
The aim of treatment is to restore blood cell production.
Non-severe AA sometimes clears up without treatment (spontaneous recovery) but this is not common. Some patients with non-severe AA may not require treatment initially if they don’t need transfusions – often referred to as ‘watch and wait’ or active monitoring. If spontaneous recovery has not happened by the time all tests have been done and treatment plans discussed, it is unlikely to happen and it is normal to start treatment is you are needing blood and/or platelet transfusions.
All patients with severe or very severe AA are likely to need blood and platelet transfusions and treatment to prevent/control infections. This is called supportive care.
There are three elements to supportive care:
- Treatment of anaemia – there are no options available to prevent anaemia but it can be treated with transfusions. Sometimes a large number of red cell transfusions can create a build-up of iron in the body, but this can be treated with drugs.
- Prevention and treatment of infection – if the neutrophil count is below normal, antibodies and antifungal drugs may be given to reduce the risk of infection. If you develop fever or any other symptoms which may indicate an infection, it is important to let your doctor or specialist nurse know immediately.
- Prevention of bleeding – Low platelet levels can make bleeding a problem. Regular transfusions can be given if the count falls below 10 x 109/L (or 20 x 109/L in the presence of fever and/or infection).
Definitive treatment aims to either control damage to bone narrow stem cells (immunosuppression) or replacing damaged stem cells with healthy cells from a donor (stem cell transplant). The choice of treatment is based on the severity of AA as well as the age and general health of the patients and the availability of a bone marrow donor.
Aplastic anemia treatments focus on increasing the number of healthy cells in your blood (blood count). When your blood counts go up, you will experience fewer symptoms and require less treatment. People who have mild or moderate aplastic anemia may not need treatment as long as the condition doesn’t get worse. People who have severe aplastic anemia need medical treatment right away to prevent complications.
People who have very severe aplastic anemia need emergency medical care in a hospital. Very severe aplastic anemia can be fatal if it’s not treated right away. Removing a known cause of aplastic anemia, such as exposure to a toxin, may cure the condition.
Treatments for aplastic anemia include blood transfusions, blood and marrow stem cell transplants, and medicines. These treatments can prevent or limit complications, relieve symptoms, and improve quality of life. Blood and marrow stem cell transplants may cure the disorder in some people who are eligible for a transplant. Removing a known cause of aplastic anemia, such as exposure to a toxin, also may cure the condition.
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