Definition
The normal platelet count in adults is determined by averaging about two standard deviations from a group of healthy individuals, and it ranges from 150,000 to 450,000/L, although the level for any individual is kept within sharp limits and narrow day by day.
A platelet count of less than 150,000/L is considered to be thrombocytopenia.
A recent 50% drop in platelet count, even when within reference ranges, may indicate serious clinical problems and requires active follow-up. However, thrombocytopenia is usually not diagnosed clinically until the platelet count has been reduced to significant levels – below 50,000/L.
Epidemiology
The definition of epidemiology depends on the cause of the disease. It should be considered that 2.5% of the normal population has a platelet count below 150,000, as mentioned above (standard deviation). The administration of heparin, when used in a prophylactic dose against venous thromboembolism, shows a risk of thrombocytopenia induced by heparin of less than 0.1%. However, when using an anticoagulant (rather than a prophylactic) dose, the risk of developing heparin-induced thrombocytopenia increases to 0.76%.
Thrombopoiesis
With a half-life of about 10 days, a blood volume of 5 L, and one-third of platelets stored in the spleen, an adult must produce, on average, about 100 billion platelets each day to maintain a normal count under normal conditions. steady, with the ability to significantly boost output in response to rising demand. The daily generation of platelets in healthy people ranges from 35,000 to 50,000/L of whole blood.
Thrombopoiesis depends on the bone marrow microenvironment, cell surface and soluble hematopoietic growth factors, especially stem cell growth factor (SCF) and thrombopoietin (Tpo), which are indispensable for normal and stimulated thrombopoiesis in vivo .
Studies have observed that platelets have an endothelial support function by connecting endothelial spaces in intact blood vessels. It is estimated that a fixed amount of platelets of 7,000/L/day is required to maintain normal hemostasis. Thus, there appears to be a baseline physiological need for platelets to prevent spontaneous bleeding. This need increases in cases of fever, sepsis, inflammation and use of certain medications.
Main Causes
Thrombocytopenia can be caused by:
1. Primary immune thrombocytopenia
It is a condition in which there is usually a decrease in the production and destruction of platelets in the blood due to antibodies produced by the body itself.
2. Use of medication
Thrombocytopenia can be a side effect of using medications such as heparin, acetaminophen or valproic acid. Some of these drugs can stimulate the production of antibodies against platelets, which lead to their destruction, or cause the body to inhibit the production of new platelets.
3. Infectious diseases
Infectious diseases such as infectious mononucleosis, caused by the Epstein-Barr virus, and HIV, can cause thrombocytopenia, usually by inhibiting the production of platelets by the bone marrow.
4. Liver diseases
Liver diseases, such as cirrhosis and infectious hepatitis, are usually associated with an enlarged spleen, which leads to increased destruction of platelets in the blood, and can also affect the production of thrombopoietin, a hormone that stimulates the production of new platelets, causing its decrease.
5. Excessive alcohol consumption
Excessive alcohol consumption may be related to cirrhosis, folic acid and vitamin B12 deficiency, which may lead to a decrease in the production of platelets by the body or their destruction by the spleen, causing thrombocytopenia.
6. Nutrient deficiencies
Deficiencies of nutrients such as folate and vitamin B12 can affect the production of cells in the blood, as in megaloblastic anemia, which can result in lower production of platelets and lead to thrombocytopenia.
7. Autoimmune diseases
Thrombocytopenia can occur associated with diseases caused by the person's own production of antibodies, such as systemic lupus erythematosus and Graves' disease, which can also cause the destruction of platelets that circulate in the blood.
8. Pregnancy
Mild thrombocytopenia can occur in pregnancy as a result of the normal changes that occur in a woman's body during this period and, when caused by these changes, it does not usually cause bleeding and tends to improve after delivery.
However, thrombocytopenia can also be a sign of other diseases such as pre-eclampsia and antiphospholipid antibody syndrome, and its evaluation by an obstetrician is recommended.
9. Cancer
Although rare, some cancers, such as leukemia and lymphoma, can cause a decrease in platelet production by affecting the bone marrow, resulting in thrombocytopenia.
10. Radiotherapy and chemotherapy
Radiotherapy and chemotherapy, which are often used to treat different types of cancer, can also affect platelet production in some cases, causing thrombocytopenia.
Identification
The amount of platelets in the blood can be identified through the CBC and normally ranges from 150,000 to 450,000/mL. Therefore, thrombocytopenia is considered when the presence of less than 150,000 platelets per mL of blood is identified.
Signs and Symptoms
-Patients with thrombocytopenia may be asymptomatic, and it is possible that thrombocytopenia will first be seen on a routine blood count.
-The symptomatic presentation of thrombocytopenia is bleeding, which usually occurs immediately after injury, initially in the skin and mucous membranes, and does not involve joints and muscles.
-There are usually no surgical bleeds just from the reduction in platelet count, at least until the platelet count is less than 50,000/L, and spontaneous and clinical bleeds do not occur until the platelet count is less than 10,000 to 20,000/L.
-Due to the absence of vascular protection offered by the submucosal tissue, mucosal bleeding can present as epistaxis, gingival bleeding, and massive bullous hemorrhages in the buccal mucosa.
-Bleeding into the skin is characterized by the appearance of petechiae, purpura (confluent petechiae) or superficial ecchymoses.
-Menorrhagia (menstrual flow that does not reduce after more than three days) and metrorrhagia (uterine bleeding between menstrual periods) are also of common incidence, and there may be persistent and profuse bleeding from superficial cuts.
-Patients with thrombocytopenia are predisposed to bleeding immediately after vascular trauma. Post-traumatic or post-surgical bleeding generally responds to local measures, but may persist for hours or days after the occurrence of minor injuries.
-There is rarely CNS bleeding, but when it occurs it is often preceded by trauma; however, it is the most common cause of death due to thrombocytopenia.
Diagnosis of Thrombocytopenia
*Blood tests to measure platelet count and clotting
*Other tests to look for disorders that can cause a low platelet count
A doctor suspects thrombocytopenia in patients who have petechiae or unusual bleeding and bruises. When a patient has a condition that potentially result in thrombocytopenia, platelet levels are frequently routinely checked. When blood tests are performed on individuals who do not have bleeding or bruising for other reasons, they may find thrombocytopenia.
Determining the cause of thrombocytopenia is essential for treating the clinical condition. Certain symptoms can help determine the cause. People usually have a fever, for example, when thrombocytopenia results from an infection. On the other hand, immune thrombocytopenia, thrombotic thrombocytopenic purpura, or hemolytic uremic syndrome usually do not cause fever.
A doctor may be able to feel an enlarged spleen during a physical examination, which indicates that the spleen is catching platelets and that the thrombocytopenia is brought on by a condition that is causing the spleen to grow.
The severity of thrombocytopenia may be assessed using an automatic counter that counts platelets, and the source of the condition can be determined by looking at a blood sample under a microscope. A sample of bone marrow taken and examined under a microscope (bone marrow aspiration and biopsy) may occasionally be needed to provide information about platelet production.
Thrombocytopenia Treatment
Management of thrombocytopenic disorders depends on treating the specific causes. The first question that arises is in patients with severe thrombocytopenia whether it is necessary to transfuse platelets.
In asymptomatic (no bleeding) patients in the setting of severe thrombocytopenia requires prophylactic platelet transfusion regardless of the underlying cause, usually below 10,000/mm³ in most afebrile patients and ≤ 15,000 to 20,000/microL in patients with known fever, infection, or inflammation due to increased risk of bleeding.
Patients with active bleeding should be transfused with platelets immediately to maintain a platelet count > 50,000/mm³ in most bleeding situations, including DIC and > 100,000/mm³ if there is central nervous system bleeding.
The suspension or maintenance of anticoagulants and antiplatelet agents in patients with an indication for use, such as arrhythmias, cardiovascular and thrombotic diseases, are evaluated according to the risk of bleeding and the benefit of using the drugs, often with a decision shared with family members and patients.
Patients with asymptomatic thrombocytopenia and a count below 50,000 should avoid high-impact physical activities, such as martial arts.
