Essential thrombocythemia
From IDWiki
Definition
- Myelodysplastic disorder of the thrombocytopoeitic stem cells causing a clonal proliferation of thrombocytes
Clinical Manifestations
- History
- History of thrombosis or bleeding
- Signs & Symptoms
- Digital ischemia
- Cerebrovascular ischemia
- High risk for vascular events if:
- History of thrombosis or bleeding
- Increased cardiovascular risk
- Older than 60 years
Differential Diagnosis
- Must distinguish from other myelodysplastic disorders (especially polycythemia vera) as well as from secondary causes of thrombocytosis
Investigations
- CBC with peripheral blood film shows thrombocytosis with platelet anisocytosis
- RBCs usually normochromic and normocytic, unless there is concurrent iron deficiency anemia
- Leukoerythroblastic picture suggests post-ET myelofibrosis
- Bone marrow aspiration and biopsy shows normal cellularity or moderate hypercellularity with large megakaryocytes
- Findings that suggest an alternative diagnosis include highly atypical megakaryocytes, increased myeloblasts, myelodysplastic features, or significant reticulin fibrosis or collagen fibrosis
- Genetic testing
- JAK2 in 60-65%
- CALR in 20-25%
- MPL in 5%
- Triple-negative (all above negative) in 10-15%
WHO Diagnostic Criteria
- Diagnosis require 4 major criteria or the first 3 major criteria plus the minor criterion
- Major criteria
- Platelets ≥450
- Bone marrow biopsy showing proliferation of megakaryocytes with increased numbers of enlarged, mature megakaryocytes with hyperlobulated nuclei; and no significant increase or left shift in neutrophil granulopoiesis or erythropoiesis and very rare minor increase in reticulin fibers
- Not meeting WHO criteria for BCR-ABL1 CML, PV, PMF, myelodysplastic syndrome, or other myeloid neoplasms
- Presence of JAK2, CALR, or MPL mutation
- Minor criterion
- Presence of a clonal marker or abscence of evidence for reactive thrombocytosis
Management
- Acute
- If digital or cerebrovascular ischemia, rapid cytoreduction with platelet pheresis
- Chronic
- If high risk, requires cytoreduction and aspirin:
- First-line: hydroxyurea
- Alternative: anagrelide
- Pregnancy: interferon alfa
- If >1.5m platelets, requires cytoreduction alone
- If high risk, requires cytoreduction and aspirin:
