Essential Thrombocythemia

Chapter 29 Essential Thrombocythemia



Ronald Hoffman, Marina Kremyanskaya, Vesna Najfeld, John Mascarenhas



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Figure 29-1 PROBABILITY OF THROMBOSIS-FREE SURVIVAL IN 114 PATIENTS WITH ESSENTIAL THROMBOCYTHEMIA TREATED WITH HYDROXYUREA OR LEFT UNTREATED.


(From Cortelazzo S, Finazzi G, Ruggeri M, et al: Hydroxyurea for patients with essential thrombocythemia and a high risk of thrombosis. N Engl J Med 332:1132, 1995.)



Table 29-1 Frequency of Neurologic Complaints Associated With Essential Thrombocythemia

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Data from Jabaily J, Iland HJ, Laszlo J, et al: Neurologic manifestations of essential thrombocythemia. Ann Intern Med 99:513, 1983.


Table 29-2 Risk Stratification in Essential Thrombocythemia Based on Thrombotic Risk*



















Risk Category Age >60 Years or History of Thrombosis Cardiovascular Risk Factors
Low No No
Intermediate No Yes
High Yes Yes

*Cardiovascular risk factors: hypertension, hypercholesterolemia, diabetes, smoking, and congestive heart failure. Extreme thrombocytosis (platelet count >1500 × 109/L) is a risk factor for bleeding. Its role as a risk factor for thrombosis in essential thrombocythemia is uncertain.


Data from Finazzi G, Barbui T: Risk-adapted therapy in essential thrombocythemia and polycythemia vera. Blood Rev 19:243, 2005.


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Figure 29-2 ESSENTIAL THROMBOCYTHEMIA (ET): PERIPHERAL BLOOD SMEAR AND BONE MARROW BIOPSY.


The peripheral blood smear in ET shows a marked thrombocytosis with anisocytosis (varying sizes) of the platelets (A). The bone marrow (B) is hypercellular and exhibits a marked proliferation of large and giant megakaryocytes in loose clusters with other hematopoietic elements in the background. The large megakaryocytes (C) tend to be extensively lobulated.


Table 29-3 Proposed Revised World Health Organization Criteria for the Diagnosis of Primary Myelofibrosis and Essential Thrombocythemia and British Committee for Standards in Hematology Criteria for Diagnosis of Essential Thrombocythemia





















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Jun 12, 2016 | Posted by in HEMATOLOGY | Comments Off on Essential Thrombocythemia

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Proposed Revised WHO Criteria for Primary Myelofibrosis
Major Criteria


1. Presence of megakaryocyte proliferation and atypia,* usually accompanied by either reticulin or collagen fibrosis or in the absence of significant reticulin fibrosis, the megakaryocyte changes must be accompanied by an increased BM cellularity characterized by granulocytic proliferation and often decreased erythropoiesis (i.e., prefibrotic cellular phase disease)


2. Not meeting WHO criteria for PV,† CML,‡ MDS,§ or other myeloid neoplasm


3. Demonstration of JAK2617V->F or other clonal marker (e.g., MPL515W->L/K) or in the absence of a clonal marker, no evidence of BM fibrosis caused by underlying inflammatory or other neoplastic diseases‖

Minor Criteria


1. Leukoerythroblastosis


2. Increase in serum LDH level


3. Anemia


4. Palpable splenomegaly

Diagnosis requires meeting all three major criteria and two minor criteria.
BM, Bone marrow; CML, chronic myeloid leukemia; LDH, lactate dehydrogenase; MDS, myelodysplastic syndrome; PV, polycythemia vera; WHO, World Health Organization.
*Small to large megakaryocytes with an aberrant nuclear-to-cytoplasmic ratio and hyperchromatic, bulbous, or irregularly folded nuclei and sense clustering.
†Requires the failure of iron replacement therapy to increase hemoglobin level to the PV range in the presence of decreased serum ferritin. Exclusion of PV is based on hemoglobin and hematocrit levels, and RBC mass measurement is not required.
‡Requires the absence of BCR-ABL.
§Requires absence of dyserythropoiesis and dysgranulopoiesis.
‖Secondary to infection, autoimmune disorder or other chronic inflammatory condition, hairy cell leukemia or other lymphoid neoplasm, metastatic malignancy, or toxic (chronic) myelopathies. It should be noted that patients with conditions associated with reactive myelofibrosis are not immune to primary myelofibrosis, and the diagnosis should be considered in such cases if other criteria are met.
Degree of abnormality could be borderline or marked.
Proposed Revised World Health Organization Criteria for Essential Thrombocythemia


1. Sustained platelet count ≥450 × 109/L*


2. BM biopsy specimen showing proliferation mainly of the megakaryocytic lineage with increased numbers of enlarged, mature megakaryocytes; no significant increase or left shift of neutrophil granulopoiesis or erythropoiesis


3. Not meeting WHO criteria for PV,† PMF,‡ CML,§ MDS,‖ or other myeloid neoplasm


4. Demonstration of JAK2V617F or other clonal marker or in the absence of a clonal marker, no evidence for reactive thrombocytosis