50 have microvascular occlusive events such as burning pain in the extremities

50 have microvascular occlusive events such as

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50% have microvascular occlusive events such as burning pain in the extremities (erythromelalgia) or digital ischaemia, major vascular occlusive events, or haemorrhage at presentation (Figure 4.3). Palpable splenomegaly may be present but is not prominent in most patients. Laboratory investigations The JAK2 V617F mutation is found in about half the cases of this disorder, and mutations in the CALR and MPL genes in a smaller proportion. Given that a molecular abnormality can be identified in approximately 85% of cases of ET, these investigations comprise an important part of the diagnostic pathway (Figure 4.4). In such cases, if PV and PMF can be ruled out, a diagnosis of ET can be confidently made. In the absence of a molecular abnormality, investigations should aim to exclude other causes of thrombocytosis. Apart from a full blood count and blood film, these should include erythrocyte sedimentation rate, serum C reactive protein, serum ferritin and bone marrow aspirate, trephine and cytogenetic analysis. Trephine histology can often reveal features such as clusters of large megakaryocytes that are suggestive of ET (Figure 4.5). Cytogenetic studies are generally normal in ET, but occasionally patients with chronic myeloid leukaemia will present with an isolated thrombocytosis, so a BCR–ABL fusion should be excluded. Certain cytogenetic abnormalities may also favour an alternative diagnosis of myelodysplasia.
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  • Spring '18
  • Mr. kanor
  • Hematology, thrombocytosis

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