Aplastic anemia
Cells require the supply of oxygen for their proper functioning. Those responsible for carrying oxygen to the tissues are the red blood cells, also called erythrocytes or red blood cells. Red cells form in the bone marrow; When there is a decrease in hematopoietic tissue, which is what gives rise to the different blood cells, including red blood cells, and there is no tumor, fibrosis or other type of process that occupies the space of the bone marrow, it is spoken of a process of aplasia, that is, a lack of production of the precursor cells that give rise to red blood cells, leukocytes and platelets.
How it is produced
When the hematopoietic tissue of the bone marrow disappears, the space that remains within the bone framework is replaced by fatty tissue.
Within the different types of aplastic anemias, the congenital ones are differentiated from the acquired ones. Among the causes of congenital aplastic anemia are:
- Fanconi anemia, an autosomal recessive hereditary disease that, in addition to anemia, presents with skin and bone malformations; it can degenerate into leukemia.
- Dyskeratosis congenita, an X-linked inherited disease associated with medullary aplasia and skin lesions.
- Diamond Blackfan syndrome, a congenital selective aplasia that only affects the cells of the red line, the red blood cells, respecting the white line (leukocytes) and the platelet.
Among the acquired causes, the following stand out:
- Drugs such as chloramphenicol, sulfa drugs, thiazides, gold salts, or tolbutamide.
- Toxic such as benzene, toluene, DDT or calcium chloride viruses such as hepatitis C, togavirus, HIV, herpes viruses or parvovirus B-19 selective acquired erythroblastopenia, in 50% of cases associated with a tumor of the thymus
In any case, it can be said that 50% of acquired aplastic anemias are of unknown origin.
Symptoms
The symptoms of aplastic anemia are the classics of an anemic syndrome, namely, pale skin and mucous membranes, asthenia, dyspnea, palpitations, headache, lack of concentration, irritability, insomnia or low libido, all consequences of poor tissue oxygenation. These symptoms are tolerated better or worse depending on the speed of onset of the medullary aplasia, generally slower in the cases of acquired aplastic anemias.
Likewise, due to the failures in the other cell lines, that of leukocytes or white blood cells and that of platelets, the patient often suffers from recurrent infections and bleeding processes.
Diagnosis
The diagnosis will be based on the questioning of the patient and laboratory data. It is convenient to detect symptoms of tiredness, paleness, dyspnea, headache or other neurological disorders. Likewise, the existence of recurrent infections or bleeding episodes and the exposure to possible causative agents such as drugs, toxic substances, radiation or infections by certain viruses should be investigated.
If anemia is suspected, a complete blood test will be performed, which should include a complete blood count, basic biochemistry, and reticulocytes. Characteristically, the red cells of aplastic anemia are larger than usual but contain a normal amount of hemoglobin; This is assessed with specific parameters, which are the mean corpuscular volume (MCV), which assesses the mean size of the red cells, and the mean corpuscular hemoglobin (HCM), which measures the mean amount of hemoglobin per red cell. Since there is an increase in MCV and normal HCM, aplastic anemia is classified as macrocytic anemia (larger cells) normochromic (normal amount of hemoglobin).
Likewise, the blood test will show a decrease in both the number of leukocytes and platelets, unless it is a selective aplasia of the red line.
The reticulocytes in the blood will also be evaluated, that is, the young forms of red cells existing in the blood, which in this case will be diminished, since the bone marrow is the affected tissue and cannot create new red cells.
The confirmatory test of aplastic anemia is provided by the bone marrow biopsy, which would allow studying the red cells in formation as well as the other cell lines and it will be seen that there is a decrease in the cells that form in it. Aplastic anemia is considered severe when the bone marrow cell occupancy is less than 30% and when, in addition, in the blood test, there are neutrophils below 500 per mm3, platelets below 20,000 per mm3 or reticulocytes below 1%.
Treatment
If a cause of aplastic anemia can be determined, such as drugs or toxins, steps will be taken to avoid exposure to them. In any case, the treatment of choice to solve marrow aplasia is bone marrow transplantation, which will cure 80% of cases. However, in advanced ages, bone marrow transplantation is not indicated, so other treatments are applied, such as high-dose corticosteroids, cytostatic drugs, red cell growth factors, or antilymphocyte globulins.
In many cases, palliative blood transfusions are the only possible treatment.
Precautionary measures
There are few preventive measures to avoid aplastic anemia except to avoid excessive exposure to drugs, toxins and radiation that can cause it.
(Updated at Apr 14 / 2024)