Platelet Functions and Pathologies

Blood is a vital element for the functioning of the human body. It has a liquid component, the plasma, where a number of important substances necessary for our life are transported, and three types of cells. Red blood cells (carry oxygen), white blood cells (perform a defensive function) and platelets.

What are platelets?

Platelets are portions of a larger cell, called a megakaryocyte, found in the blood factory (bone marrow). Each megakaryocyte, when fragmented, produces hundreds of platelets that pass into the blood. These, having no nucleus, cannot divide or reproduce. They usually last in the blood for about 9 days.

Platelets help to protect us from bleeding. There are continually small breaks in the blood vessels that are plugged by platelets. Platelets have the ability to detect the rupture or injury of a blood vessel and bind, immediately helping to stop the bleeding. Subsequently, they help to initiate blood clotting so that the plugging of the blood loss is more effective.

According to hematology specialists, platelets are indispensable to ensure the integrity of blood circulation by stopping bleeding. The normal number of platelets is between 120,000 and 400,000 per microliter of blood. Generally, it is necessary to investigate the platelet count when it is below 100,000 or above 500,000 on a repeated basis.

Platelet-related problems

There are three types of platelet-related problems:

  • Thrombocytopenia, i.e., having fewer platelets than normal. This is the most frequent problem, however, most of the time it has no repercussions because frequently, even if we have fewer platelets, these are capable of ensuring correct hemostasis (normal blood circulation without bleeding). If the number of platelets is very low, the patient will have problems of bruising and bleeding.
  • Thrombocytosis, i.e. having more platelets than normal. The increase in the number of platelets is a physiological defense mechanism in case of inflammation and infection. Therefore, in these cases the platelet count may be higher than normal. If the platelet count is excessively high, there is an increased risk of thrombosis. The clearest example of this problem occurs in a blood disease called essential thrombocythemia, in which the patient may have 2 to 5 times the normal platelet count. Another frequent cause of high platelets is low iron, a situation that should always be assessed in these patients.
  • Thrombocytopathy, i.e., having malfunctioning platelets. Although the number may be normal, there is a tendency to hemorrhage. Most of this platelet malfunction is due to the administration of drugs. This administration may be intentional (to improve circulation or prevent thrombosis) or be an adverse effect of a drug.
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Most frequent diseases associated with platelets

  • Thrombocytopenia or gestational plateletopenia: thrombocytopenia means “low platelet count”. A common cause is a drop in platelets seen in many pregnant women. It does not usually need treatment. The problem is that if the drop is significant, epidural anesthesia cannot be administered because of the risk of bleeding.
  • Primary immune thrombocytopenia: also called Idiopathic Thrombocytopenic Purpura. It is a drop in platelets generally of immunological cause (our body destroys our own platelets due to an autoimmune disorder). Frequently the drop in platelets is not serious. When it is, treatment with cortisone and sometimes immunoglobulins is usually necessary. Recently, new treatments have become available for patients who do not respond, such as thrombopag and romiplostin.
  • Essential Thrombocythemia: It is a benign tumor of platelets that are produced in an uncontrolled manner and if left untreated can lead to thrombosis. Treatment has two objectives, one is to prevent thrombosis with small doses of aspirin, and the second is to reduce the platelet count when it has reached dangerous levels, generally with hydroxyurea.
  • Thrombocytopenia or plateletopenia secondary to cancer treatments: this is one of the most frequent causes of low platelets. They are usually due to the effect of chemotherapy on the blood factory. When the drop in platelets is compromised, platelet transfusions are necessary.

Are there platelet transfusions?

Yes, there are. They are available from blood donors and are available from blood banks or transfusion services. They can be obtained from a normal blood donation or from a special platelet donation. In the first case it is necessary to separate the platelets from the red blood cells and by pooling this fraction from several donors we obtain a sufficient quantity of platelets to transfuse (usually from 5 donors). In the second case with an apheresis machine we can obtain platelets from a single donor of higher quality.