Blood platelet count too high

If the platelets in the blood are elevated (>500. 000/μl), this is called thrombocytosis. These can be either primary (congenital, genetic) or secondary (acquired, caused by another disease).

Secondary thrombocytosis is usually caused by infections, chronic inflammatory diseases, tissue injuries or certain forms of anaemia. Infections in which elevated platelet levels occur: Pneumonia, meningitis, kidney inflammation, joint inflammation and bone inflammation, but also gastrointestinal infections or blood poisoning are conceivable causes. During the infection, there is usually an increased consumption of thrombocytes, so the number of platelets drops for the time being.

Subsequently, the release of messenger substances (cytokines) leads to an increased expression of thrombopoietin (stimulates thrombocyte formation) and thus to an excessive production of blood platelets (rebound effect). This effect can also occur, for example, after chemotherapy or autoimmune diseases. Not only acute but also chronic inflammation can lead to this cytokine increase.

These include, for example, rheumatism, inflammation of the intestines (Crohn’s disease, ulcerative colitis) or tissue injuries after accidents or burns. Another cause of thrombocytosis is certain types of anaemia. These include haemolytic anaemia (anaemia caused by bleeding), sickle cell disease and thalassemia (changes in red blood cells).

These diseases result in less functioning erythrocytes, which in turn leads to a lack of oxygen in the tissues. This ultimately leads to cytokine release. The cytokines then again increase the formation of thrombocytes.

Primary thrombocytosis can also be caused by various factors. These are inherited diseases (familial primary thrombocytosis) or malignant diseases of the bone marrow (e.g. chronic myeloid leukaemia). Even after removal of the spleen, the values can increase because the storage organ is no longer present.

But even in healthy people, temporarily elevated platelet levels can occur. This can have emotional causes, such as stress or fear. But physical exertion can also lead to a temporary increase, which is particularly common during pregnancy.

This temporary increase is usually due to the fact that the spleen, which stores up to 30% of the thrombocytes, releases more of them. The effect of an increased thrombocyte count is increased blood clotting. Patients have an increased risk of thrombus formation.

This can lead to secondary diseases such as leg vein thrombosis, stroke, splenic infarction, pulmonary embolism or the development of acute myeloid leukaemia. A blood platelet deficiency or surplus can be very easily diagnosed by taking a blood sample and subsequent examination in a laboratory. This can be done in hospital or at the family doctor as a routine check and usually takes only a few minutes.

The blood is then automatically examined in the laboratory and a so-called “blood count” is produced. In addition to the blood platelet count, this contains the erythrocyte and leukocyte count, as well as a number of other parameters (inflammation values, thyroid gland values, etc.). In total, over 500 different parameters can be determined. Usually one simply distinguishes between a “small blood count” and a “large blood count”. The tested values are usually the same everywhere, although there are usually small differences between the clinics.