Thrombocythemia

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Thrombocythemia
Other namesThrombocytosis
Specialty Hematology   OOjs UI icon edit-ltr-progressive.svg
Histopathological image representing a bone marrow aspirate in a patient with essential thrombocythemia Essential thrombocythemia (1).jpg
Histopathological image representing a bone marrow aspirate in a patient with essential thrombocythemia

Thrombocythemia is a condition of high platelet (thrombocyte) count in the blood. Normal count is in the range of 150,000 to 450,000 platelets per microlitre of blood. [1] but investigation is only considered if the upper limit exceeds 750,000.

Contents

When the cause is unknown, the term thrombocythemia is used, as either primary thrombocythyemia or essential thrombocythemia. The condition arises from a fault in the bone marrow cells that overproduce the platelets. The cause of the fault is unknown, and this type is not common. [2]

When the cause is known such as another disorder or disease, the term thrombocytosis is preferred, as either secondary or reactive thrombocytosis. Reactive thrombocytosis is the most common type and though it can often have no symptoms it can sometimes predispose to thrombosis. In contrast, thrombocytopenia refers to abnormally low blood platelet numbers in the blood. [2]

Signs and symptoms

High platelet levels do not necessarily signal any clinical problems, and are picked up on a routine full blood count. However, it is important that a full medical history be elicited to ensure that the increased platelet count is not due to a secondary process. Often, it occurs in tandem with an inflammatory disease, as the principal stimulants of platelet production (e.g. thrombopoietin) are elevated in these clinical states as part of the acute phase reaction.High platelet counts can occur in patients with polycythemia vera (high red blood cell counts), and is an additional risk factor for complications.[ citation needed ]

A very small number of people report symptoms of erythromelalgia, a burning sensation and redness of the extremities that resolves with cooling, or aspirin or both. [3]

Scientific literature sometimes excludes thrombocytosis from the scope of thrombophilia by definition, [4] but practically, by the definition of thrombophilia as an increased predisposition to thrombosis, [5] [6] thrombocytosis (especially primary thrombocytosis) is a potential cause of thrombophilia. Conversely, secondary thrombocytosis very rarely causes thrombotic complications. [7]

Causes

Reactive thrombocythemia is the most common cause of a high platelet count. It accounts for 88% to 97% of thrombocythemia cases in adults, and 100% in children. In adults, acute infection, tissue damage, chronic inflammation and malignancy are the common causes of reactive thrombocythemia. Usually, one or more of these conditions is present in more than 75% of the cases with reactive thrombocythemia. Causes for reactive thrombocytopenia in children are similar to adults. In addition to that, haemolytic anemia and thalassemia are often present in children living in the Middle East. Other causes of reactive thrombocythemia include: post surgery, iron deficiency, drugs, and rebound effect after bone marrow suppression. [8]

Once the reactive causes of thrombocythemia are ruled out, clonal thrombocythemia should be considered. The most common cause of clonal thrombocythemia is a myeloproliferative neoplasm. These include: essential thrombocythemia, chronic myelogenous leukemia, polycythemia vera, and primary myelofibrosis. [8]

Extremely rare causes of thrombocythemia are spurious causes. This is due to the presence of structures resembling platelets in the blood such as needle-like cryoglobulin crystals, cytoplasmic fragments of circulating leukemic cells, bacteria, and red blood cell microvesicles. These structures are counted as platelets by the automated machine counter; therefore, causing the platelet number to be falsely elevated. However, such error can be avoided by doing a peripheral blood smear. [8]

Diagnosis

Laboratory tests might include: full blood count, liver enzymes, renal function and erythrocyte sedimentation rate.[ citation needed ]

If the cause for the high platelet count remains unclear, bone marrow biopsy is often undertaken, to differentiate whether the high platelet count is reactive or essential.[ citation needed ]

Treatment

Often, no treatment is required or necessary for reactive thrombocytosis. In cases of reactive thrombocytosis of more than 1,000x109/L, it may be considered to administer daily low dose aspirin (such as 65 mg) to minimize the risk of stroke or thrombosis. [9]

However, in essential thrombocythemia, if platelet counts are over 750,000 or 1,000,000, and especially if there are other risk factors for thrombosis, treatment may be needed. Selective use of aspirin at low doses is thought to be protective. Extremely high platelet counts can be treated with hydroxyurea (a cytoreducing agent) or anagrelide (Agrylin). [10]

In Janus kinase 2 positive disorders, ruxolitinib (Jakafi) can be effective.[ citation needed ]

Related Research Articles

Blood cell Cell produced by hematopoiesis

A blood cell, also called a hematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Together, these three kinds of blood cells add up to a total 45% of the blood tissue by volume, with the remaining 55% of the volume composed of plasma, the liquid component of blood.

Thrombosis Vascular disease caused by the formation of a blood clot inside a blood vessel

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.

Platelet Component of blood aiding in coagulation

Platelets, also called thrombocytes, are a component of blood whose function is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot. Platelets have no cell nucleus; they are fragments of cytoplasm that are derived from the megakaryocytes of the bone marrow, which then enter the circulation. Circulating unactivated platelets are biconvex discoid (lens-shaped) structures, 2–3 µm in greatest diameter. Activated platelets have cell membrane projections covering their surface. Platelets are found only in mammals, whereas in other vertebrates, thrombocytes circulate as intact mononuclear cells.

Thrombotic thrombocytopenic purpura human disease

Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, heart, and brain dysfunction. Symptoms may include large bruises, fever, weakness, shortness of breath, confusion, and headache. Repeated episodes may occur.

Polycythemia vera human disease

Polycythemia vera is an uncommon myeloproliferative neoplasm in which the bone marrow makes too many red blood cells. It may also result in the overproduction of white blood cells and platelets.

Polycythemia Human disease

Polycythemia is a disease state in which the hematocrit and/or hemoglobin concentration are elevated in peripheral blood.

Thrombocytopenia blood platelet disease characterized by a low platelet count

Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood.

Megakaryocyte large bone marrow cell responsible for the production of platelets

A megakaryocyte is a large bone marrow cell with a lobated nucleus responsible for the production of blood thrombocytes (platelets), which are necessary for normal blood clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but can increase in number nearly 10-fold during the course of certain diseases. Owing to variations in combining forms and spelling, synonyms include megalokaryocyte and megacaryocyte.

Hydroxycarbamide chemical compound

Hydroxycarbamide, also known as hydroxyurea, is a medication used in sickle-cell disease, chronic myelogenous leukemia, cervical cancer, and essential thrombocythemia. In sickle-cell disease it increases fetal hemoglobin and decreases the number of attacks. It is taken by mouth.

Essential thrombocythemia human disease

Essential thrombocythemia (ET) is a rare chronic blood cancer characterised by the overproduction of platelets (thrombocytes) by megakaryocytes in the bone marrow. It may, albeit rarely, develop into acute myeloid leukemia or myelofibrosis. It is one of four myeloproliferative neoplasms that occur when the body makes too many white or red blood cells, or platelets).

Heparin-induced thrombocytopenia development of thrombocytopenia (a low platelet count), due to the administration of various forms of heparin, an anticoagulant

Heparin-induced thrombocytopenia (HIT) is the development of thrombocytopenia, due to the administration of various forms of heparin, an anticoagulant. HIT predisposes to thrombosis because platelets release microparticles that activate thrombin, thereby leading to thrombosis. When thrombosis is identified the condition is called heparin-induced thrombocytopenia and thrombosis (HITT). HIT is caused by the formation of abnormal antibodies that activate platelets. If someone receiving heparin develops new or worsening thrombosis, or if the platelet count falls, HIT can be confirmed with specific blood tests.

Thrombophilia abnormality of blood coagulation that increases the risk of thrombosis (blood clots in blood vessels)

Thrombophilia is an abnormality of blood coagulation that increases the risk of thrombosis. Such abnormalities can be identified in 50% of people who have an episode of thrombosis that was not provoked by other causes. A significant proportion of the population has a detectable thrombophilic abnormality, but most of these develop thrombosis only in the presence of an additional risk factor.

Plateletpheresis

Plateletpheresis is the process of collecting thrombocytes, more commonly called platelets, a component of blood involved in blood clotting. The term specifically refers to the method of collecting the platelets, which is performed by a device used in blood donation that separates the platelets and returns other portions of the blood to the donor. Platelet transfusion can be a life-saving procedure in preventing or treating serious complications from bleeding and hemorrhage in patients who have disorders manifesting as thrombocytopenia or platelet dysfunction. This process may also be used therapeutically to treat disorders resulting in extraordinarily high platelet counts such as essential thrombocytosis.

Primary myelofibrosis (PMF) is a rare bone marrow blood cancer. It is classified by the World Health Organization (WHO) as a type of myeloproliferative neoplasm, a group of cancers in which there is abnormal growth of cells in the bone marrow. This overproduction is most often associated with a somatic mutation in the JAK2, CALR, or MPL gene markers. In PMF, the healthy marrow is replaced by scar tissue (fibrosis), resulting in a lack of production of normal blood cells. Symptoms include anemia, increased infection and an enlarged spleen (splenomegaly).

Myeloproliferative neoplasm hematopoietic disorders that derive from the blood-forming stem cells of the bone marrow

Myeloproliferative neoplasms (MPNs) are a group of rare blood cancers in which excess red blood cells, white blood cells or platelets are produced in the bone marrow. Myelo refers to the bone marrow, proliferative describes the rapid growth of blood cells and neoplasm describes that growth as abnormal and uncontrolled.

Anagrelide chemical compound

Anagrelide is a drug used for the treatment of essential thrombocytosis, or overproduction of blood platelets. It also has been used in the treatment of chronic myeloid leukemia.

Hypercoagulability in pregnancy is the propensity of pregnant women to develop thrombosis. Pregnancy itself is a factor of hypercoagulability, as a physiologically adaptive mechanism to prevent post partum bleeding. However, when combined with an additional underlying hypercoagulable states, the risk of thrombosis or embolism may become substantial.

Basophilia

Basophilia is the condition of having greater than 200 basophils/μL in the venous blood.

Hematologic diseases are disorders which primarily affect the blood & blood-forming organs. Hematologic diseases include rare genetic disorders, anemia, HIV, sickle cell disease & complications from chemotherapy or transfusions.

Prefibrotic primary myelofibrosis (Pre-PMF) is a rare blood cancer, classified by the World Health Organization as a distinct type of myeloproliferative neoplasm in 2016. The disease is progressive to overt primary myelofibrosis, though the rate of progression is variable and not all patients progress. Symptoms and presentation can mimic essential thrombocythemia, with the main differentiator for pre-PMF being the presence of fibrosis in the bone marrow.

References

  1. Kumar & Clark (2005). "8". Clinical Medicine (Sixth ed.). Elsevier Saunders. pp.  469. ISBN   0-7020-2763-4.
  2. 1 2 "Thrombocythemia and Thrombocytosis | National Heart, Lung, and Blood Institute (NHLBI)". www.nhlbi.nih.gov. Retrieved 20 December 2019.
  3. van Genderen, P. J.; Lucas, I. S.; van Strik, R.; Vuzevski, V. D.; Prins, F. J.; van Vliet, H. H.; Michiels, J. J. (1996-09-01). "Erythromelalgia in essential thrombocythemia is characterized by platelet activation and endothelial cell damage but not by thrombin generation". Thrombosis and Haemostasis. 76 (3): 333–338. doi:10.1055/s-0038-1650579. ISSN   0340-6245. PMID   8883266.
  4. "Management of patients with thrombophilia". Drug and Therapeutics Bulletin. 33 (1): 6–8. 1995. doi:10.1136/dtb.1995.3316. PMID   7587981. S2CID   44647401.
  5. Mitchell RS, Kumar V, Abbas AK, Fausto N (2007). "Chapter 4". Robbins Basic Pathology (Eighth ed.). Philadelphia: Saunders. ISBN   978-1-4160-2973-1.
  6. Heit JA (2007). "Thrombophilia: common questions on laboratory assessment and management". Hematology Am. Soc. Hematol. Educ. Program. 2007 (1): 127–35. doi: 10.1182/asheducation-2007.1.127 . PMID   18024620.
  7. Pediatric Thrombocytosis at eMedicine
  8. 1 2 3 Jonathan, S Bleeker; William, J Hogan (8 June 2011). "Thrombocytosis: Diagnostic Evaluation, Thrombotic Risk Stratification, and Risk-Based Management Strategies". Thrombosis. 2011: 536062. doi:10.1155/2011/536062. PMC   3200282 . PMID   22084665.
  9. Secondary Thrombocytosis~treatment at eMedicine
  10. Harrison, CN; Campbell PJ; Buck G; Wheatley K; East CL; Bareford D; Wilkins BS; van der Walt JD; Reilly JT; Grigg AP; Revell P; Woodcock BE; Green AR; United Kingdom Medical Research Council Primary Thrombocythemia 1 Study (2005). "Hydroxyurea compared with anagrelide in high-risk essential thrombocythemia". NEJM. 353 (1): 33–45. doi:10.1056/NEJMoa043800. PMID   16000354.
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