JAK2 or CALR mutation status defines subtypes of essential thrombocythemia with substantially different clinical course and outcomes

Elisa Rumi, Daniela Pietra, Virginia Ferretti, Thorsten Klampfl, Ashot S. Harutyunyan, Jelena D. Milosevic, Nicole C C Them, Tiina Berg, Chiara Elena, Ilaria C. Casetti, Chiara Milanesi, Emanuela Sant'Antonio, Marta Bellini, Elena Fugazza, Maria C. Renna, Emanuela Boveri, Cesare Astori, Cristiana Pascutto, Robert Kralovics, Mario Cazzola

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Patients with essential thrombocythemia may carry JAK2 (V617F), an MPL substitution, or a calreticulin gene (CALR) mutation. We studied biologic and clinical features of essential thrombocythemia according to JAK2 or CALR mutation status and in relation to those of polycythemia vera. The mutant allele burden was lower in JAK2-mutated than in CALR-mutated essential thrombocythemia. Patients with JAK2 (V617F) were older, had a higher hemoglobin level and white blood cell count, and lower platelet count and serum erythropoietin than those with CALR mutation. Hematologic parameters of patients with JAK2-mutated essential thrombocythemia or polycythemia vera were related to the mutant allele burden. While no polycythemic transformation was observed in CALR-mutated patients, the cumulative risk was 29% at 15 years in those with JAK2-mutated essential thrombocythemia. There was no significant difference in myelofibrotic transformation between the 2 subtypes of essential thrombocythemia. Patients with JAK2-mutated essential thrombocythemia and those with polycythemia vera had a similar risk of thrombosis, which was twice that of patients with the CALR mutation. These observations are consistent with the notion that JAK2-mutated essential thrombocythemia and polycythemia vera represent different phenotypes of a single myeloproliferative neoplasm, whereas CALR-mutated essential thrombocythemia is a distinct disease entity.

Original languageEnglish
Pages (from-to)1544-1551
Number of pages8
Issue number10
Publication statusPublished - Mar 6 2014


ASJC Scopus subject areas

  • Hematology
  • Biochemistry
  • Cell Biology
  • Immunology

Cite this

Rumi, E., Pietra, D., Ferretti, V., Klampfl, T., Harutyunyan, A. S., Milosevic, J. D., Them, N. C. C., Berg, T., Elena, C., Casetti, I. C., Milanesi, C., Sant'Antonio, E., Bellini, M., Fugazza, E., Renna, M. C., Boveri, E., Astori, C., Pascutto, C., Kralovics, R., & Cazzola, M. (2014). JAK2 or CALR mutation status defines subtypes of essential thrombocythemia with substantially different clinical course and outcomes. Blood, 123(10), 1544-1551. https://doi.org/10.1182/blood-2013-11-539098