Chapter 29 Essential Thrombocythemia
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
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.
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
| 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 |
| 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¶ |
