Each person has between 150,000 and 450,000 platelets (thrombocytes) per microliter of blood. Platelets play an important role in our body, especially for blood clotting. When the level of platelets falls below 150,000, we speak of thrombocytopenia (thrombocytopenia). The term thus describes a deficiency of blood platelets. The opposite of thrombocytopenia is called thrombocytosis.
Function of platelets
Our blood is composed of a liquid component, blood plasma, and various solid components, blood cells. In total, there are three types of blood cells in the blood: the erythrocytes (red blood cells), the leukocytes (white blood cells), and the platelets (thrombocytes). The platelets are particularly important for our blood clotting: if a vessel is injured, the platelets close the injured area by attaching themselves to the vessel wall from the inside as well as to each other. The activity of the platelets results in the formation of the scab in open injuries. Normally, this process takes no longer than six minutes.
Causes of thrombocytopenia
Thrombocytopenia can have many different causes. The lack of platelets may be caused by a platelet formation disorder, by a shortened platelet life span, or by a distribution disorder. If an educational disorder is the cause of thrombocytopenia, a distinction must be made between congenital and acquired educational disorders. Congenital formation disorders include diseases such as TAR syndrome, Fanconi anemia, or May-Hegglin anomaly. Acquired educational disorders, on the other hand, include bone marrow diseases such as leukemia, bone marrow damage, or substrate deficiency such as folic acid or vitamin B12 deficiency. If a shortened platelet life span is the cause of thrombocytopenia, it may be caused by mechanical damage to the platelets, for example. Such mechanical damage can be caused, for example, by artificial heart valves. In addition, increased blood clotting and an antibody reaction can also lead to a shortened life span of the platelets. In around ten percent of women, thrombocytopenia also occurs towards the end of pregnancy – although this is usually only mild and disappears after birth. This thrombocytopenia, which occurs in the last third of pregnancy, usually has no consequences for the child. If there are no symptoms and no underlying disease, this indicates pseudothrombocytopenia: This occurs because the platelets clump together on their way to the laboratory and are thus no longer identified as platelets by the counting equipment in the laboratory, but as leukocytes. Thus, a decreased platelet count and an increased leukocyte count are diagnosed, even though the blood counts are fine.
Immune thrombocytopenia
In immune thrombocytopenia (ITP) – an autoimmune disease – a shortened life span of platelets is the cause of thrombocytopenia. A distinction is made between an acute form, known as acute immune thrombocytopenia, which primarily affects children, and a chronic form, known as chronic immune thrombocytopenia. Chronic immune thrombocytopenia is said to occur after a period of six months. In chronic immune thrombocytopenia, the lack of platelets occurs because the immune system mistakenly recognizes platelets as foreign substances and produces antibodies. These cause the breakdown of platelets by the spleen to accelerate, shortening their life span.
Heparin-induced thrombocytopenia.
Another cause of thrombocytopenia may be treatment with heparin. Heparin is a drug used to inhibit blood clotting and prevent the development of thrombosis. In heparin-induced thrombocytopenia, two different types are distinguished. In type I, the number of platelets decreases spontaneously due to interactions caused by treatment with heparin. Normally, however, the low platelet count rises again on its own after a few days. In heparin-induced type II thrombocytopenia, the platelet count decreases due to antibody formation triggered by the administration of the heparin. As a result, blood clotting is not inhibited but further activated and blood clots are formed.These blood clots can then lead to a stroke or pulmonary embolism, for example. In addition, the formation of clots can cause the baseline platelet count to decrease by more than half.
Symptoms of thrombocytopenia
If the value falls below 150,000 platelets per microliter of blood, this is not noticeable at first. This is because even with significantly lower platelet levels, the body does not initially react with symptoms of failure. However, thrombocytopenia is noticeable in that it takes longer than usual, i.e. longer than six minutes, for smaller injuries to close. A characteristic feature of thrombocytopenia is an increased bleeding tendency in those affected. Typical symptoms include small skin hemorrhages (petechial skin hemorrhages) in the subcutis. In addition, nose and gum bleeding and bruising may also occur more frequently. With extremely low platelet levels (< 30,000), the bleeding tendency increases further and mucosal bleeding occurs more frequently. In particularly severe cases, internal bleeding may also occur.
Treating thrombocytopenia
If thrombocytopenia is present, the type of therapy used depends primarily on the underlying cause. In rare cases – when the lack of platelets becomes life-threatening, the number of platelets can be increased by transfusion. However, this method carries the risk of intolerance as well as infection. In addition, platelet transfusion is very expensive. In addition, thrombocytopenia can also be treated by medication. For example, the active ingredient eltrombopag ensures that the production of platelet precursor cells is stimulated – which leads to an increase in the number of platelets in the long term.
