Aplastic anemia is a disease whose main manifestation is a significant impairment of the three components of the hematopoietic system (the system that creates blood components): the red line – creates red blood cells containing hemoglobin, the white line – creates white blood cells, and the platelet line – is responsible for blood clotting. As a result of this impairment, there is a significant decrease in the components of the three lines in the bone marrow and peripheral blood.
The natural environment in which the components of the hematopoietic system develop is called the “microenvironment”. There is a reciprocal relationship between the stem cells that are the source of the development of the hematopoietic system and their natural environment. These relationships are figuratively called “seed and soil”. The mechanism that causes the development of aplastic anemia is the failure of stem cells due to a defect in them themselves, or due to factors acting in the “microenvironment” such as attack by the immune system, or a lack of growth factors that stimulate the development of the hematopoietic system. The disease can develop due to congenital or acquired causes.
The incidence of the disease in the United States ranges from 0.5 to 1 per 1,000,000, and the highest rate is in people aged 15-30 and over 60. There is no difference in its incidence in men and women.
Congenital aplastic anemia syndromes:
- Fanconi syndrome – a hereditary disorder that is also manifested by congenital skeletal defects and a tendency to malignancies;
- Shwachman-Diamond syndrome – which is also accompanied by pancreatic failure and a malabsorption syndrome;
- Dyskeratosis congenita – appears, with rare exceptions, only in males and is accompanied by a skin syndrome;
Aplastic Anemia Symptoms
Symptoms are associated with the gradual development of bone marrow failure, and include: pallor, weakness and fatigue due to anemia (decreased hemoglobin level), signs of bleeding due to thrombocytopenia (decreased platelet count) and infections secondary to neutropenia (decreased white blood cell count – leukocytes).
Causes and Risk Factors
Causes of Acquired Aplastic Anemia:
- Medications – Certain medications may cause the development of aplastic anemia depending on the dose of the drug, such as chemotherapy. Other medications may cause aplastic anemia due to hypersensitivity, such as certain antibiotics, anti-inflammatory drugs or the blood thinner ticlopidine.
- Radiation therapy, especially in high doses or with prolonged exposure.
- Exposure to certain chemicals such as benzene.
- Infection with certain viruses, especially hepatitis B virus (a virus that causes liver disease), EBV, provirus and HIV.
- Pregnancy may rarely cause aplastic anemia.
- Autoimmune diseases such as lupus are sometimes associated with the development of aplastic anemia.
Diagnosis and tests
The diagnosis is made using the peripheral blood surface, which can monitor a decrease in the three blood lines, as well as through a bone marrow biopsy, which can demonstrate a depletion of all elements of the hematopoietic system, and a relative increase in the percentage of fat cells. There are indicators for the diagnosis of severe aplastic anemia, based on the peripheral blood picture and bone marrow, with their findings indicating a sharp decrease in the three blood lines.
Aplastic Anemia Treatments
The treatment of aplastic anemia consists of supportive care and disease-directed treatment. Most patients, if they receive only supportive care without treatment directed at the disease itself, will die within a year or two. Supportive care includes the administration of blood products and long-term antibiotic therapy. Targeted treatment includes bone marrow transplantation from a donor (preferably from a sibling, but also possible from a foreign donor), or treatment that suppresses the immune system and growth factors.
Bone marrow transplantation is effective in 60%-90% of patients. The degree of success of the treatment depends on the patient’s age, the availability of the donor, and the degree of compatibility between the donor and the recipient. The main complications of this treatment are failure of the graft to accept and graft-versus-host disease. This is a serious disease caused by the graft attacking the body systems of the patient, the recipient of the graft (the host).
If a transplant from a donor is not possible, it is customary to treat with immunosuppressants. This choice is based on the positive relationship between overactivity of the immune system and the development of the disease.
The common drugs for suppressing the immune system are: (ATG – Anti Thymocytic Globulin), Cyclosporine (Cyclosporine A), and Corticosteroids. The response rate (partial and complete) of these combinations is 70%-80%, but only between a quarter and a third of patients respond completely.
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What’s Next?
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