Essential Haematology is established as the most authoritative introduction to haematology. Beautifully presented, it introduces the formation and function of blood cells and diseases that arise from dysfunction and disruption of these processes. Basic science, diagnostic tests, clinical features and management are all clearly explained. The book outlines the basic principles of clinical and laboratory haematology and shows how manifestations of blood diseases can be explained by new knowledge of the disease processes.
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Hoffbrand's Essential Haematology is widely regarded as the most authoritative introduction to the subject available, helping medical students and trainee doctors understand the essential principles of modern clinical and laboratory haematology for nearly four decades. Now in its eighth edition, this market-leading textbook introduces the formation and function of blood cells and the diseases that arise from dysfunction and disruption of these processes.
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1 ReviewReviews aren't verified, but Google checks for and removes fake content when it's identifiedWrite reviewEssentials in Hematology and Clinical PathologyBy Ramadas Nayak, Sharada Rai, Astha Gupta if (window['_OC_autoDir']) _OC_autoDir('search_form_input');About this book
Essential thrombocytosis is also known as essential thrombocythemia (ET) and was formerly known as hemorrhagic thrombocythemia and is one of the myeloproliferative neoplasms. Myeloproliferative neoplasms include polycythemia vera, primary myelofibrosis, and essential polycythemia; these neoplasms are similar and share the same mutations. Essential thrombocytosis is characterized by thrombocytosis and megakaryocytic hyperplasia of the bone marrow. According to the World Health Organization, essential thrombocytosis can be diagnosed when the platelet count is over 45,0000 and there is either a Janus kinase 2 (JAK2), Calreticulin (CALR) or myeloproliferative leukemia virus oncogene (MPL) mutation, lacking clonal or reactive causes. This activity describes the presentation, cause, management, and potential complications of essential thrombocytosis and reviews the role of the interprofessional team in caring for patients with this disease.
Objectives:Identify the typical presentation of essential thrombocytosis.Describe the evaluation of a patient withessential thrombocytosis.Summarize the treatment options for essential thrombocytosis.Explain the role of the interprofessional interprofessional team in coordinating the evaluation and management of this condition.Access free multiple choice questions on this topic.
Essential thrombocytosis is also known as essential thrombocythemia (ET). It was first recognized in 1934; however, at that time, it was described as hemorrhagic thrombocythemia. Essential thrombocytosis is one of the myeloproliferative neoplasms. It was classified as a myeloproliferative neoplasm in 1951 by Damesheck.[1] Myeloproliferative neoplasm includes polycythemia vera, primary myelofibrosis, and essential polycythemia.[2] The three types of myeloproliferative neoplasm are similar as they share the same mutations. Approximately 55% of patients with essential thrombocytosis have the JAK2 mutation.[3] Essential thrombocytosis is characterized by thrombocytosis with the presence of megakaryocytic hyperplasia in the bone marrow. Due to thrombocytosis, there are risks of vascular events such as thrombosis and hemorrhage and sometimes the conversion to a blast phase of myelofibrosis.[4] According to the World Health Organization, essential thrombocytosis is a disease that occurs when the platelet count is more than 450000 with the presence of Janus kinase 2 (JAK2), Calreticulin (CALR) or myeloproliferative leukemia virus oncogene (MPL) mutation, lacking clonal or reactive causes.[5] This review article will focus on reviewing the etiology, epidemiology, pathophysiology, evaluation, and treatment of this disease.
The primary cause of essential thrombocythemia is the overproduction of hematopoietic cells due to the mutation of JAK2, CALR or MPL gene. These genes are known as driver mutations due to the role they play in the development of a myeloproliferative neoplasm.[6]
Essential thrombocytosis is the most common type of myeloproliferative neoplasm. Reports are that 1.0 to 2.5 individuals per 100000 have essential thrombocytosis yearly.[7] The prevalence was reported to be 38 to 57 per 100000 between 2008 and 2010 and mostly occurring in females.[8] The incidence of essential thrombocytosis increases with age, with most patients presenting between the ages of 50 and 60.
The driver genes JAK2, CALR, and MPL, have specific functions which when mutated cause myeloproliferative effects. In 2005, research showed that a single point mutation of the JAK2 leads to a myeloproliferative neoplasm.[9] The point mutation causes a change in the amino acid from valine to phenylalanine at codon 617, hence, the abbreviation JAK2V617F.[10] JAK 2 is a non-receptor tyrosine kinase found in the cytoplasm playing a pivotal role in hematopoiesis. Its mutation aids in the gain of function leading to the activation of intracellular signaling pathways associated with the receptors of hematopoietic cytokines: erythropoietin, thrombopoietin, and granulocyte colony-stimulating factor.[6] About half of patients with essential thrombocytosis have JAK2 mutation.[6] CALR mutation occurs due to insertions or deletions causing a shift in the amino acid reading frame which leads to the formation of a novel C terminus.[6] CALR is normally involved in cellular proliferation, differentiation, and apoptosis.[10] MPL gene, on the other hand, is reported to be mutated via point mutation and about 3 to 15% of essential thrombocytosis patients are affected by this mutation.[10]
The bone marrow cellularity helps define essential thrombocytosis. In essential thrombocytosis, the bone marrow microscopic examinations show clustered enlarged megakaryocytes with matured cytoplasm containing multilobulated nuclei.[4]
Essential thrombocytosis patients could present with variable symptoms. In asymptomatic patients, thrombocytosis is usually an incidental finding on complete blood count. For symptomatic patients, the most common symptoms are migraines, headache, and dizziness.[7] They can also present with various levels of thrombosis including hepatic vein thrombosis which is the hallmark of the disease, or they can present with symptoms like transient ischemic attack, erythromelalgia, and easy bruising.[7] The most common physical finding in essential thrombocytosis is splenomegaly, which is mild when compared to other myeloproliferative neoplasms.[7]
The evaluation of patients with essential thrombocytosis includes getting a complete blood count, a bone marrow biopsy and genetic testing to evaluate for gene mutations. Platelet count should be more than 450000. The bone marrow biopsy should show evidence of increased proliferation of the megakaryocytic cell lines with increased numbers of enlarged, matured megakaryocytes. Because the symptoms of myeloproliferative neoplasms overlap, it is important to also rule out other causes of thrombocytosis, including clonal and reactive causes, before reaching a definite diagnosis of essential thrombocytosis.[11] To differentiate from reactive thrombocytosis, it is recommended to get acute phase reactants and an iron panel. The abnormality in these two has been shown to cause thrombocytosis. In the inflammatory process, there will be an elevation of acute phase reactant such as CRP which has been reported as elevated in a patient with reactive thrombocytosis.[12] Once there is resolution of inflammation, thrombocytosis is expected to resolve. Also in iron deficiency, thrombocytosis is expected to resolve with iron repalcement.
It is helpful to recognize which genetic mutation a patient has whether it is JAK2, CALR or MPL because each of these mutations determines the clinical features, complications, and survival of myeloproliferative neoplasm.[10] Research shows that genetic testing will help to determine the phenotype and prognosis of essential thrombocytosis. For instance, a patient with CALR mutations of essential thrombocytosis has a better prognosis.[13] The presence of a mutation strengthens the diagnosis of all myeloproliferative neoplasms as 97% of patients have some form of mutations, whether JAK2, CALR, or MPL.[13]
The goal of treatment of essential thrombocytosis is to prevent vascular complications such as thrombotic and hemorrhagic events; this is because thrombosis and hemorrhage are the leading causes of morbidity and mortality.[14] Risk stratification is used to determine whether the patient should receive treatment or not. Therefore, treatment strategy depends on whether the patient is low or high risk for thrombosis. Low-risk patients are young (under age 60) with no prior thrombosis, and high-risk patients are as older (over age 60) with a previous history of thrombosis.[12] For a low-risk patient, it is recommended to treat with aspirin if there are no major contraindications for aspirin. There should be careful consideration of possible acquired von Willebrand syndrome when platelets are more than 1000 x 10^9/L. In the setting of abnormal von Willebrand laboratory parameters and/or bleeding aspirin should not be used. For a patient with microvascular thrombosis event such as erythromelalgia, aspirin is also the indicated treatment. For a high-risk patient, antiplatelet and cytoreductive therapy is the choice.
Hydroxyurea is the first line cytoreductive therapy used. If not well tolerated or patient is resistance to hydroxyurea, then anagrelide is used. Hydroxyurea has been shown to reduce both the number of platelets and the number of leukocytes causing a reduction in thrombosis and myelofibrosis.[1] Anagrelide, on the other hand, is a second line therapy used to reduce platelet count. It does this by inhibiting the differentiation of megakaryocytes and platelet aggregation.[1] Compared to hydroxyurea, anagrelide is superior in preventing venous thrombosis, but it increases the rate of hemorrhage when combined with aspirin. Other drugs used in essential thrombocytosis include radioactive phosphorous, pipobroman, interferon, and busulfan.[1] These are still used in older patients who cannot tolerate hydroxyurea. Many clinical trials have proven the use of cytoreductive therapy to reduce the number of thrombotic events including the one reported by Cortelazzo et al. (1995). Cortelazzo et al. followed high risks patients taking either hydroxyurea or placebo for 6 months, and he found that 3.6% of patients receiving hydroxyurea suffered from thrombotic events compared to the 24% of people not taking hydroxyurea in the placebo group.[15] For pregnant patients with essential thrombocytosis, it is recommended to use low molecular weight heparin during pregnancy for 6 weeks after delivery as well as cytoreduction with pegylated interferon.[1] Also, in pregnant females who have extremely high platelets, the action of interferon is slow to bring down the platelets; plateletpheresis was reported to be an option to reduce the number of platelets.[16] 2ff7e9595c
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