Introduction
Aplastic anaemia is a group of different diseases whose common feature is a weakness (insufficiency) of the bone marrow, which leads to a reduced production of blood cells. This not only leads to anaemia, i.e. a reduction in red blood cells (erythrocytes) or haemoglobin levels, but also to a deficiency in the formation of immune cells, especially the so-called neutrophilic granulocytes (neutropenia), as well as blood platelets (thrombopenia). If all three cell groups mentioned are affected, this is called pancytopenia. In most cases the cause is autoimmune diseases, but aplastic anaemia can also be caused by chemotherapy or be congenital.
What causes aplastic anemia?
Aplastic anaemia, also known as panmyelopathy, is not a uniform disease, but a group of different diseases and syndromes, which ultimately lead to a deficient formation of blood cells due to weakness of the bone marrow. Causes of such bone marrow insufficiency can generally be congenital or acquired, although the acquired forms are much more common. Among the congenital forms, Fanconi anemia and Diamond-Blackfan syndrome are particularly noteworthy, as well as other rare enzyme defects.
Among the triggers of acquired aplastic anaemia are primarily autoimmune reactions against the bone marrow, the cause of which is often not identifiable. Other haematological diseases such as myelodysplastic syndrome (MDS) are also involved. Another important trigger is certain drugs, in particular cytostatic drugs used in chemotherapy have a toxic effect on the bone marrow, as they often have to be given in high doses.
Other drugs that in rare cases can lead to aplastic anaemia include metamizole (Novalgin) or the neuroleptic clozapine. The effect of the majority of chemotherapeutic drugs is that they attack rapidly dividing cells, i.e. mainly cancer cells. However, they also attack other cells in the body, including stem cells in the bone marrow that form blood cells, so that these cells drop during chemotherapy.
Normally, however, the bone marrow is not completely destroyed, but regenerates after the end of therapy. However, in rare cases and depending on the treatment protocol, it is possible that the bone marrow does not recover after chemotherapy and aplastic anaemia may occur. Aplastic anaemia can be caused not only by cytostatic drugs but also by other drugs.
Important examples are metamizole (Novalgin) and the neuroleptic clozapine. Bone marrow failure is independent of the dose, it is based on the body’s hypersensitivity to certain substances. Although this side effect is extremely rare, it must be taken into account, especially when these drugs are given for the first time or in high doses!
Symptoms of Aplastic Anemia
The symptoms of aplastic anaemia are caused by the deficiency of the respective blood cells. There are three so-called blood cell lines: When there is a deficiency of erythrocytes, the cells in the entire body can no longer be supplied with oxygen as well. The main consequences are feelings of weakness, circulatory problems, paleness and ringing in the ears.
This is treated from a critical Hb value onwards with the transfusion of so-called erythrocyte concentrates. A lack of leukocytes cannot be subjectively noticed by the patient, but it is the most dangerous effect of aplasia. This is mainly due to a subgroup of white blood cells, the neutrophil granulocytes.
If these are missing, neutropenia occurs. The patient is no longer sufficiently protected from opportunistic pathogens – i.e. pathogens that are actually relatively harmless and only become dangerous when the immune system is weakened. Even normal infections can then proceed very drastically and become life-threatening.
A thrombocyte deficiency is also often not noticed at first. Due to the poorer coagulation, bruising can occur more quickly. However, it becomes dangerous when the thrombocytes are very low, which can lead to dangerous internal bleeding. – the red blood cells (erythrocytes), mainly responsible for oxygen transport
- The white blood cells (leukocytes), cells of the immune system
- The blood platelets (thrombocytes), part of the blood clotting system
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