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      Polycythemia Vera: Thinking Beyond the Hematocrit

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      , MS, PA-C
      Journal of the Advanced Practitioner in Oncology
      Harborside Press LLC

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          Abstract

          Polycythemia vera is a Philadelphia chromosome–negative myeloproliferative neoplasm that results in increased myeloproliferation. It is a debilitating disease characterized by the overproduction of red blood cells, but it also can result in increased white blood cells and platelets. Patients experience a shortened overall survival due to an increased risk of thrombotic events, including stroke, myocardial infarction, pulmonary embolism, and deep vein thrombosis. Current treatment strategies in clinical practice are driven by mitigating the risk of these thrombotic events by reducing patients’ hematocrit. In addition to thrombosis risk, polycythemia vera patients have constitutional symptoms such as fatigue, itching, bone pain, erythromelalgia, and splenomegaly. An increased risk of transformation of their disease to acute myeloid leukemia and/or myelofibrosis can also affect long-term survival in polycythemia vera. Additional research has identified other risk factors, such as increased white blood cells, increased platelet count, and cytokine levels, which can alter the prognosis of the disease. In this review, we will discuss the current treatment strategies in polycythemia vera and determine if incorporating additional biomarkers as endpoints is feasible in clinical practice.

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          Most cited references39

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          The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia.

          The World Health Organization (WHO) classification of tumors of the hematopoietic and lymphoid tissues was last updated in 2008. Since then, there have been numerous advances in the identification of unique biomarkers associated with some myeloid neoplasms and acute leukemias, largely derived from gene expression analysis and next-generation sequencing that can significantly improve the diagnostic criteria as well as the prognostic relevance of entities currently included in the WHO classification and that also suggest new entities that should be added. Therefore, there is a clear need for a revision to the current classification. The revisions to the categories of myeloid neoplasms and acute leukemia will be published in a monograph in 2016 and reflect a consensus of opinion of hematopathologists, hematologists, oncologists, and geneticists. The 2016 edition represents a revision of the prior classification rather than an entirely new classification and attempts to incorporate new clinical, prognostic, morphologic, immunophenotypic, and genetic data that have emerged since the last edition. The major changes in the classification and their rationale are presented here.
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            A gain-of-function mutation of JAK2 in myeloproliferative disorders.

            Polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis are clonal myeloproliferative disorders arising from a multipotent progenitor. The loss of heterozygosity (LOH) on the short arm of chromosome 9 (9pLOH) in myeloproliferative disorders suggests that 9p harbors a mutation that contributes to the cause of clonal expansion of hematopoietic cells in these diseases. We performed microsatellite mapping of the 9pLOH region and DNA sequencing in 244 patients with myeloproliferative disorders (128 with polycythemia vera, 93 with essential thrombocythemia, and 23 with idiopathic myelofibrosis). Microsatellite mapping identified a 9pLOH region that included the Janus kinase 2 (JAK2) gene. In patients with 9pLOH, JAK2 had a homozygous G-->T transversion, causing phenylalanine to be substituted for valine at position 617 of JAK2 (V617F). All 51 patients with 9pLOH had the V617F mutation. Of 193 patients without 9pLOH, 66 were heterozygous for V617F and 127 did not have the mutation. The frequency of V617F was 65 percent among patients with polycythemia vera (83 of 128), 57 percent among patients with idiopathic myelofibrosis (13 of 23), and 23 percent among patients with essential thrombocythemia (21 of 93). V617F is a somatic mutation present in hematopoietic cells. Mitotic recombination probably causes both 9pLOH and the transition from heterozygosity to homozygosity for V617F. Genetic evidence and in vitro functional studies indicate that V617F gives hematopoietic precursors proliferative and survival advantages. Patients with the V617F mutation had a significantly longer duration of disease and a higher rate of complications (fibrosis, hemorrhage, and thrombosis) and treatment with cytoreductive therapy than patients with wild-type JAK2. A high proportion of patients with myeloproliferative disorders carry a dominant gain-of-function mutation of JAK2. Copyright 2005 Massachusetts Medical Society.
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              Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders.

              Human myeloproliferative disorders form a range of clonal haematological malignant diseases, the main members of which are polycythaemia vera, essential thrombocythaemia, and idiopathic myelofibrosis. The molecular pathogenesis of these disorders is unknown, but tyrosine kinases have been implicated in several related disorders. We investigated the role of the cytoplasmic tyrosine kinase JAK2 in patients with a myeloproliferative disorder. We obtained DNA samples from patients with polycythaemia vera, essential thrombocythaemia, or idiopathic myelofibrosis. The coding exons of JAK2 were bidirectionally sequenced from peripheral-blood granulocytes, T cells, or both. Allele-specific PCR, molecular cytogenetic studies, microsatellite PCR, Affymetrix single nucleotide polymorphism array analyses, and colony assays were undertaken on subgroups of patients. A single point mutation (Val617Phe) was identified in JAK2 in 71 (97%) of 73 patients with polycythaemia vera, 29 (57%) of 51 with essential thrombocythaemia, and eight (50%) of 16 with idiopathic myelofibrosis. The mutation is acquired, is present in a variable proportion of granulocytes, alters a highly conserved valine present in the negative regulatory JH2 domain, and is predicted to dysregulate kinase activity. It was heterozygous in most patients, homozygous in a subset as a result of mitotic recombination, and arose in a multipotent progenitor capable of giving rise to erythroid and myeloid cells. The mutation was present in all erythropoietin-independent erythroid colonies. A single acquired mutation of JAK2 was noted in more than half of patients with a myeloproliferative disorder. Its presence in all erythropoietin-independent erythroid colonies demonstrates a link with growth factor hypersensitivity, a key biological feature of these disorders. Identification of the Val617Phe JAK2 mutation lays the foundation for new approaches to the diagnosis, classification, and treatment of myeloproliferative disorders.
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                Author and article information

                Journal
                J Adv Pract Oncol
                J Adv Pract Oncol
                J Adv Pract Oncol
                JADPRO
                Journal of the Advanced Practitioner in Oncology
                Harborside Press LLC
                2150-0878
                2150-0886
                July 2023
                1 July 2023
                : 14
                : 5
                : 405-413
                Affiliations
                [1]From Arizona School of Health Sciences, Mesa, Arizona
                Author notes
                Correspondence to: Matthew Waggoner, MS, PA-C, Arizona School of Health Sciences, 5850 E Still Circle, Mesa, AZ 85206 E-mail: mwaggon624@ 123456gmail.com
                Article
                2023.14.5.5
                10.6004/jadpro.2023.14.5.5
                10414534
                9256b36b-83f9-4249-ae8e-60e0fee75cd4
                © 2023 Harborside™

                This article is distributed under the terms of the Creative Commons Attribution Non-Commercial Non-Derivative License, which permits unrestricted non-commercial and non-derivative use, distribution, and reproduction in any medium, provided the original work is properly cited.

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