Each human has between 150,000 and 450,000 platelets (platelets) per microliter of blood. Platelets play an important role in our body, especially for blood clotting. If it falls below the value of 150,000 platelets, it is called a thrombocytopenia (thrombocytopenia). The term thus describes a lack of platelets. The opposite of thrombocytopenia is called thrombocytosis.
Function of platelets
Our blood is composed of a liquid component, the blood plasma, and various solid components, the blood cells. In total, there are three types of blood cells in the blood: red blood cells, red blood cells, white blood cells and platelets.
The thrombocytes are especially important for our blood clotting: If a vessel is injured, the platelets seal the injured site by the inside of the vessel wall and store each other. Due to the activity of the platelets, wound scabs develop in open wounds. Normally, this process does not take longer than six minutes.
Causes of thrombocytopenia
Thrombocytopenia can have many different causes. Platelet deficiency may be caused by platelet formation disorder, shortened platelet life, or a distributional disorder.
If an educational disorder is the cause of thrombocytopenia, a distinction must be made between a congenital and an acquired disorder. Congenital disorders of education include diseases such as TAR syndrome, Fanconi anemia, or the May-Hegglin anomaly. On the other hand, the acquired disorders include bone marrow diseases such as leukemia, bone marrow damage or a lack of substrate such as a deficiency of folic acid or vitamin B12.
If a shortened life of the platelets is the cause of thrombocytopenia, this may have been caused, for example, by a mechanical damage to the platelets. Such mechanical damage can occur, for example, through artificial heart valves. In addition, increased blood coagulation and an antibody reaction can lead to a shortened platelet lifetime.
In around ten percent of women also thrombocytopenia occurs towards the end of pregnancy - but this is usually only slightly pronounced and forms after birth back. Consequences for the child, thrombocytopenia occurring in the last trimester of pregnancy usually has no.
If there are no symptoms and no underlying disease, this indicates a pseudothrombocytopenia. This is caused by the fact that the platelets on the way to the laboratory clump together and are therefore no longer identified by the counting devices in the laboratory as a platelet, but as a leukocyte. Thus, a decreased platelet count and an increased white blood cell count are diagnosed, although the blood levels are in order.
In the case of immune thrombocytopenia (ITP) - an autoimmune disease - a shortened platelet life is the cause of thrombocytopenia. A distinction is made between an acute form, the so-called acute immune thrombocytopenia, which primarily affects children, and a chronic form, the chronic immune thrombocytopenia. Chronic immune thrombocytopenia is referred to as a six-month period.
In chronic immune thrombocytopenia, the lack of platelets occurs because the immune system erroneously recognizes the platelets as foreign substances and forms antibodies. These ensure that the degradation of the platelets by the spleen accelerates and thus their life is shortened.
Another cause of thrombocytopenia may be heparin treatment. Heparin is an agent used to inhibit blood clotting and prevent the development of thrombosis. There are two different types of heparin-induced thrombocytopenia. In Type I, the number of platelets decreases spontaneously because of interactions with heparin. Normally, however, the low platelet count will automatically increase after a few days.
In heparin-induced thrombocytopenia type II, the number of platelets decreases by antibody formation, which is triggered by the administration of heparin. As a result, the blood clotting is not inhibited, but further activated and it comes to blood clots. For example, these blood clots can lead to a stroke or pulmonary embolism. In addition, the initial formation of the platelets may decrease by more than half due to the formation of clots.
Symptoms of thrombocytopenia
If the value falls below 150,000 platelets per microliter of blood, this is initially not noticeable. Even at significantly lower platelet levels, the body does not initially react with deficits. However, thrombocytopenia is noticeable in that the occlusion of minor lesions lasts longer than usual, that is, longer than six minutes.
Characteristic of a thrombocytopenia is an increased bleeding tendency of those affected. Typical symptoms include, for example, small skin bleeding (petechial skin bleeding) in the subcutaneous tissue. In addition, bleeding of the nose and gums as well as bruising may occur more frequently. At extremely low platelet counts (<30,000), the tendency to bleed continues to increase, with frequent mucosal haemorrhages. In particularly severe cases, it can also lead to internal bleeding.
If thrombocytopenia is present, the type of therapy depends primarily on the underlying cause. In rare cases - when platelet deficiency becomes life-threatening, the number of platelets can be increased by transfusion. However, there is a risk of intolerance and infection with this method. In addition, platelet transfusion is very expensive.
In addition, thrombocytopenia can also be treated by medication. The drug eltrombopag, for example, ensures that the production of the precursor cells of the platelets is stimulated - which leads in the long term to an increase in the number of platelets.