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Encyclopedia > Essential thrombocytosis
Essential thrombocytosis
Classification & external resources
ICD-10 D75.2, D47.3
ICD-9 289.9
ICD-O: 9962/3
OMIM 187950
DiseasesDB 4522
MedlinePlus 000543
eMedicine med/2266 
MeSH D013920

Essential thrombocytosis (ET, also known as essential thrombocythemia) is a rare chronic blood disorder characterized by the overproduction of platelets by megakaryocytes in the bone marrow in the absence of an alternative cause. In some cases this disorder may be progressive, and rarely may evolve into acute myeloid leukemia or myelofibrosis. It is one of four myeloproliferative disorders. The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) is a coding of diseases and signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or diseases, as classified by the World Health Organization (WHO). ... // C00-D48 - Neoplasms (C00-C14) Malignant neoplasms, lip, oral cavity and pharynx (C00) Malignant neoplasm of lip (C01) Malignant neoplasm of base of tongue (C02) Malignant neoplasm of other and unspecified parts of tongue (C03) Malignant neoplasm of gum (C04) Malignant neoplasm of floor of mouth (C05) Malignant neoplasm of... // C00-D48 - Neoplasms (C00-C14) Malignant neoplasms, lip, oral cavity and pharynx (C00) Malignant neoplasm of lip (C01) Malignant neoplasm of base of tongue (C02) Malignant neoplasm of other and unspecified parts of tongue (C03) Malignant neoplasm of gum (C04) Malignant neoplasm of floor of mouth (C05) Malignant neoplasm of... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... The International Classification of Diseases for Oncology (ICD-O) is a domain specific extension of the International Statistical Classification of Diseases and Related Health Problems for tumor diseases. ... The Mendelian Inheritance in Man project is a database that catalogues all the known diseases with a genetic component, and - when possible - links them to the relevant genes in the human genome. ... The Disease Bold textDatabase is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... MedlinePlus (medlineplus. ... eMedicine is an online clinical medical knowledge base that was founded in 1996. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... The myeloproliferative diseases (MPDs) are a group of diseases of the bone marrow where excess cells are produced. ... A 250 ml bag of newly collected platelets. ... The megakaryocyte is a bone marrow cell responsible for the production of blood platelets when its cytoplasm becomes fragmented. ... This article does not cite any references or sources. ... Acute myeloid leukemia (AML), also known as acute myelogenous leukemia, is a cancer of the myeloid line of white blood cells, characterized by the rapid proliferation of abnormal cells which accumulate in the bone marrow and interfere with the production of normal blood cells. ... Myelofibrosis with myeloid metaplasia, also known as agnogenic myeloid metaplasia, chronic idiopathic myelofibrosis, and primary myelofibrosis,[1] was first described in 1879 and is currently classified as a myeloproliferative disease caused by the growth and proliferation of an abnormal bone marrow stem cell, resulting in the replacement of the bone... The myeloproliferative diseases (MPDs) are a group of diseases of the bone marrow where excess cells are produced. ...

Contents

Epidemiology

Essential thrombocytosis is diagnosed at a rate of about 2 to 3 per 100,000 individuals annually.[1][2] The disease usually affects middle aged to elderly individuals, with an average age at diagnosis of 50-60 years, although it can affect children and young adults as well.[3]


Pathophysiology

The pathologic basis for this disease is unknown. However, essential thrombosis resembles polycythemia vera in that cells of the megakaryocytic series are more sensitive to growth factors. Platelets derived from the abnormal megakaryocytes do not function properly, which contributes to the clinical features of bleeding and thrombosis. Polycythemia is a condition in which there is a net increase in the total circulating erythrocyte (red blood cell) mass of the body. ... The megakaryocyte is a bone marrow cell responsible for the production of blood platelets when its cytoplasm becomes fragmented. ... Growth factor is any of about twenty small proteins that attach to specific receptors on the surface of stem cells in bone marrow and promote differentiation and maturation of these cells into morphotic constituents of blood. ...


In 2005, a mutation in the JAK2 kinase (V617F) was found by multiple research groups [4][5] [6] to be associated with essential thrombocytosis in around 30% of cases. JAK2 is a member of the Janus kinase family. This mutation may be helpful in making a diagnosis or as a target for future therapy. JAK2 (Janus kinase 2 (a protein tyrosine kinase)) is a human gene that encodes for a protein called Janus kinase 2, a tyrosine kinase of the non-receptor type, involved in interleukin 3 signal transduction. ... Janus kinase< (JAK) is a family of intracellular non-receptor tyrosine kinases, ranging from 120-140 kDa, that transduce cytokine-mediated signals via the JAK-STAT pathway. ...


Clinical features

The major symptoms are bleeding and thrombosis. Other symptoms include epistaxis (nosebleeds) and bleeding from gums and gastrointestinal tract. One characteristic symptom is throbbing and burning of the hands and feet due to the occlusion of small arterioles by platelets (erythromelalgia). An enlarged spleen (splenomegaly) may be found on examination. Nosebleed as a result of fracture through a rugby impact. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Erythromelalgia, also known as Mitchells disease (after Silas Weir Mitchell) and red neuralgia(also referred to as man on fire), is a rare disorder in which blood vessels, usually in the extremities and especially in the feet, are blocked and inflamed, causing a painful burning and throbbing sensation and... Splenomegaly is an enlargement of the spleen, which usually lies in the left upper quadrant (LUQ) of the human abdomen. ...


Diagnostic criteria

The diagnosis of essential thrombocytosis requires the presence of a persistent thrombocytosis of greater than 600 x109/L in the absence of an alternative cause.


The following revised diagnostic criteria for essential thrombocytosis were proposed in 2005 [7]. The diagnosis requires the presence of both A criteria together with B3 to B6, or of criterion A1 together with B1 to B6.

  • A1. Platelet count > 600 x 109/L for at least 2 months
  • A2. Acquired V617F JAK2 mutation present
  • B1. No cause for a reactive thrombocytosis
    • normal inflammatory indices
  • B2. No evidence of iron deficiency
    • stainable iron in the bone marrow or normal red cell mean corpuscular volume
  • B3. No evidence of polycythemia vera
    • hematocrit < midpoint of normal range or normal red cell mass in presence of normal iron stores
  • B4. No evidence of chronic myeloid leukemia

But the Philadelphia chromosome may be present in up to 10% of cases. Patients withe the Philadelphia chromosome have a potential for the development of acute leukemia, especially acute lymphocytic leukemia. Polycythemia is a condition in which there is a net increase in the total circulating erythrocyte (red blood cell) mass of the body. ...

  • B5. No evidence of myelofibrosis
    • no collagen fibrosis and ≤ grade 2 reticulin fibrosis (using 0–4 scale)
  • B6. No evidence of a myelodysplastic syndrome
    • no significant dysplasia
    • no cytogenetic abnormalities suggestive of myelodysplasia

Myelofibrosis with myeloid metaplasia, also known as agnogenic myeloid metaplasia, chronic idiopathic myelofibrosis, and primary myelofibrosis,[1] was first described in 1879 and is currently classified as a myeloproliferative disease caused by the growth and proliferation of an abnormal bone marrow stem cell, resulting in the replacement of the bone...

Treatment

Not all patients will require treatment at presentation. In those who are at increased risk of thrombosis or bleeding (older age, prior history of bleeding or thrombosis, or very high platelet count), reduction of the platelet count to the normal range can be achieved using hydroxyurea (also known as hydroxycarbamide), interferon-α or anagrelide. Low-dose aspirin is widely used to reduce the risk of thrombosis, but there may be an increased risk of bleeding if aspirin is initiated whilst the platelet count is very high. Hydroxyurea chemical structure Hydroxyurea or hydroxycarbamide (rINN), (brand names include Hydrea®) is an antineoplastic drug used in hematological malignancies. ... Anagrelide (Agrylin®/Xagrid®, Shire) is a drug used for the treatment of essential thrombocytosis (ET; essential thrombocythemia). ...


The PT1 study [8] compared hydroxyurea in combination with aspirin to anagrelide in combination with Aspirin as initial therapy for essential thrombocytosis. Hydroxyurea was superior, with lower risk of arterial thrombosis, lower risk of severe bleeding and lower risk of transformation to myelofibrosis (although the rate of venous thrombosis was higher with hydroxycarbamide than with anagrelide).


In rare cases where patients have life-threatening complications, the platelet count can be reduced rapidly using platelet apheresis (a procedure that removes platelets from the blood directly). Whole blood enters the centrifuge on the left and separates into layers so that selected components can be drawn off on the right. ...


Prognosis

Essential thrombocytosis is a slowly progressive disorder with long asymptomatic periods punctuated by thrombotic or hemorrhagic events.


Special care related to pregnancy

Hydroxyrea and anagrelide are counter-indicated during pregnancy and nursing. There is current debate as to the safety of interferon during pregnancy and nursing. Essential thrombocytosis can be linked with increased risk of spontaeous abortion or miscarriage in the first trimester of pregnancy. Throughout pregnancy, close monitoring of the mother for thrombosis and placenta is recommended to ensure blood clots are caught. Post partum, often daily injections of low dose low molecular weight heparin (e.g. enoxaparin) are prescribed for several weeks as this is a period where the mother is at higher risk of developing a blood clot. Anagrelide (Agrylin®/Xagrid®, Shire) is a drug used for the treatment of essential thrombocytosis (ET; essential thrombocythemia). ... This article needs additional references or sources for verification. ... Nursing is a profession focused on assisting individuals, families, and communities in attaining, re-attaining, and maintaining optimal health and functioning. ... Interferons (IFNs) are natural proteins produced by the cells of the immune system of most vertebrates in response to challenges by foreign agents such as viruses, bacteria, parasites and tumor cells. ... In medicine, low molecular weight heparin (LMWH) is a class of medication used as an anticoagulant in diseases that feature thrombosis, as well as for prophylaxis in situations that lead to a high risk of thrombosis. ... Enoxaparin is a low molecular weight heparin manufactured by Sanofi-Aventis. ...


References

  1. ^ Mesa R, Silverstein M, Jacobsen S, Wollan P, Tefferi A (1999). "Population-based incidence and survival figures in essential thrombocythemia and agnogenic myeloid metaplasia: an Olmsted County Study, 1976-1995.". Am J Hematol 61 (1): 10-5. PMID 10331505. 
  2. ^ Kutti J, Ridell B (2001). "Epidemiology of the myeloproliferative disorders: essential thrombocythaemia, polycythaemia vera and idiopathic myelofibrosis.". Pathol Biol (Paris) 49 (2): 164-6. PMID 11317963. 
  3. ^ Hoffman: Hematology: Basic Principles and Practice, 4th ed., 2005 Churchill Livingstone, Chapter 71.
  4. ^ Kralovics R, Passamonti F, Buser AS, Teo SS, et al (2005 Apr 28). "A gain-of-function mutation of JAK2 in myeloproliferative disorders". N Engl J Med 352 (17): 1779-90. 
  5. ^ Baxter EJ et al. Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders. Lancet. 2005;365:1054-61. PMID 15781101
  6. ^ Levine RL et al. Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis. Cancer Cell. 2005;7:387-97. PMID 15837627
  7. ^ Campbell PJ, Green AR. Management of Polycythemia Vera and Essential Thrombocythemia. Hematology (Am Soc Hematol Educ Program). 2005;:201-8. PMID 16304381
  8. ^ Harrison CN et al. Hydroxyurea compared with anagrelide in high-risk essential thrombocythemia. N Engl J Med. 2005;7:33-45. PMID 16000354.

External links


  Results from FactBites:
 
eMedicine - Thrombocytosis : Article by Susumu Inoue (4632 words)
Primary thrombocytosis is a component of a myeloproliferative disorder (eg, essential thrombocythemia, myelofibrosis with myeloid metaplasia, polycythemia vera, chronic myelocytic leukemia [rare]) or, in rare cases, of acute myelocytic leukemia.
In pediatrics, primary thrombocytosis is exceedingly rare, whereas secondary, or reactive, thrombocytosis is common, particularly in infants.
Older children with thrombocytosis with thrombosis (suspected or demonstrated) or a history of thrombosis, increased bleeding tendency despite thrombocytosis, or splenomegaly must promptly be referred to a hematologist.
  More results at FactBites »

 
 

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