Essential thrombocythaemia ( ET ) is a rare chronic blood condition characterized by platelet excess (thrombocyte) by megakaryocytes in the bone marrow. Perhaps, although rare, develops into acute myeloid leukemia or myelofibrosis. It is one of four myeloproliferative neoplasms (a blood disorder that occurs when the body makes too many white or red blood cells, or platelets).
Video Essential thrombocythemia
Signs and symptoms
Most people with asymptomatic essential thrombocythemia at diagnosis are usually performed after recording an elevated platelet count in a complete regular blood count (CBC). The most common symptoms are bleeding (due to dysfunctional platelets), blood clots (eg, deep vein thrombosis or pulmonary emboli), headache, nausea, vomiting, abdominal pain, visual impairment, dizziness, fainting and numbness in the extremities; the most common signs are an increase in the number of white blood cells, reduced red blood cell count, and an enlarged spleen.
Maps Essential thrombocythemia
Cause
In ET, megakaryocytes are more sensitive to growth factors. Platelets are derived from activated abnormal megakaryocytes, which, along with increased platelet counts, contribute to the possibility of blood clot formation. Increased likelihood of bleeding when platelet counts greater than 1 million is due to von Willebrand (vWF) factor sequestration by an increase in platelet mass, leaving insufficient vWF for platelet adhesion. Mutations in JAK2 kinase (V617F) are present in 40-50% of cases and are diagnostic if present. JAK2 is a member of the Janus kinase family.
In 2013, two groups detected calreticulin mutations in the majority of JAK2-negative/MPL-negative patients with essential thrombocythaemia and primary myelofibrosis, making the second most common CALR mutation in myeloproliferative neoplasms. All mutations (insertions or deletions) affect the last exon, resulting in a shift in the frame of readings of the resulting protein, which creates a new terminal peptide and leads to loss of endoplasm retention of KDEL retention signals.
Diagnosis
The following revised diagnostic criteria for essential thrombocythaemia were proposed in 2005. Diagnosis requires the presence of both A criteria along with B3 to B6, or A1 criteria along with B1 to B6. The criteria are as follows:
- A1. Platelet count & gt; 450 ÃÆ'â € "10 3 /Ã,ÂμL for at least 2 months.
- A2. Acquired V617F JAK2 mutation present
- B1. There is no cause of reactive thrombocytosis
- normal inflammatory index
- B2. There is no evidence of iron deficiency
- stainable iron in bone marrow or normal red blood cells means volume
- B3. There is no evidence of polycythemia vera
- hematocrit & lt; the midpoint of normal range or normal red blood cell mass in the presence of a normal iron store
- B4. There is no evidence of chronic myeloid leukemia
- But Philadelphia chromosomes can be present in up to 10% of cases. Patients with the Philadelphia chromosome have potential for the development of acute leukemia, especially acute lymphocytic leukemia.
- B5. No evidence of myelofibrosis
- no collagen fibrosis and <= grade 2 fibrosis reticulin (using a scale of 0-4)
- B6. There is no evidence of myelodysplastic syndrome
- no significant dysplasia
- there are no cytogenetic abnormalities that show myelodysplasia
Treatment
Indication
Not all affected will require care at presentation. People are usually split into low and high risk for bleeding/blood clotting groups (based on their age, their medical history, their blood count and lifestyle), low-risk individuals are usually treated with aspirin, while those at high risk are given hydroxycarbamide and/or other treatments that reduce platelet count (such as interferon- and anagrelide).
Agent
Hydroxycarbamide, interferon-? and anagrelide may decrease platelet count. Low-dose aspirin is used to reduce the risk of blood clot formation unless the platelet count is very high, where there is a risk of bleeding from the disease, and hence this measure will be counter-productive because aspirin use increases the risk of bleeding.
The PT1 study compared hydroxyurea plus aspirin with anagrelide plus aspirin as initial therapy for ET. Patients treated with hydroxyurea have a lower incidence of arterial thrombosis, a lower incidence of severe bleeding and a lower incidence of transformation in mielofibrosis, but the risk of venous thrombosis is higher with hydroxycarbamide compared with anagrelide. It is not known whether the results apply to all ET patients. In people with ET symptoms and very high platelet counts (over 1 million), plateletpheresis can be used to remove platelets from the blood to reduce the risk of thrombosis.
Prognosis
Essential thrombocythaemia is sometimes described as a slow progressive disorder with long asymptomatic periods interspersed by thrombotic or haemorrhagic events. However, well-documented medical regimens can reduce and control platelet counts, which reduces the risk of these thrombotic or hemorrhagic events. The lifespan of well-controlled ETs is within the expected range for people of the same age but without ET. ET is the myeloproliferative neoplasm that is least likely to develop into acute myeloid leukemia.
Epidemiology
The incidence of ET is 0.6-2.5/100.000 per year, the median age at onset is 65-70 years and more often in women than in men. The incidence in children is 0.09/100,000 per year.
Pregnancy
Hydroxycarbamide and anagrelide are contraindicated during pregnancy and lactation. Essential thrombocythaemia may be associated with a threefold increase in the risk of miscarriage. During pregnancy, close monitoring of the mother and fetus is recommended. Low dose low molecular weight heparin (eg enoxaparin) may be used. For life-threatening complications, platelet counts can be rapidly reduced by platelet theresis, a procedure that removes platelets from the blood and returns the rest to the patient.
References
External links
- MacMillan Cancer Thrombocytosis Support Page
- Important Thrombocythemical Facts
Source of the article : Wikipedia
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