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Understanding Myeloproliferative Neoplasms (MPNs)

Myeloproliferative neoplasms (MPNs) are rare but potentially life-threatening diseases that burden patients greatly with debilitating symptoms and organ damage, such as bone marrow fibrosis and splenomegaly.1 Because MPNs are rare, "orphan" diseases with few treatment options, there is an urgent unmet therapeutic need.

Formerly known as myeloproliferative diseases (MPDs), MPNs are a heterogeneous group of clonal disorders derived from multipotent hematopoietic myeloid progenitors. MPNs include myelofibrosis (MF), polycythemia vera (PV), and essential thrombocythemia (ET).2,3 The incidence of MPNs is approximately 5 cases per 100,000 persons worldwide and the incidence is higher in persons aged >70 years. In this population, the incidence is 22 to 45 cases per 100,000 persons.4

The need to treat is urgent. Precise diagnosis of MPNs is challenging, yet essential to treatment.

Classification of MPNs

Classification of MPNs: Focus on MF, PV, and ET

According to the World Health Organization (WHO), Myeloproliferative neoplasms (MPNs) are divided into two large groups with similar pathophysiology and symptomatology: those that are Philadelphia chromosome-positive [Ph(+)],* such as chronic myeloid leukemia (CML), and those that are Ph(-) negative.1

Converse to CML, MPNs that are Ph(-) are not derived from a single molecular event but rather from a plethora of molecular abnormalities that culminate in aberrant cell proliferation.2,3

* Also referred to as BCR-ABL1-positive.

Also referred to as BCR-ABL1-negative.

References
  1. Vardiman JW, Thiele J, Arber DA, et al. The 2008 revision of the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia: rationale and important changes. Blood. 2009;114(5):937-951.
  2. Tefferi A, Skoda R, Vardiman JW. Myeloproliferative neoplasms: contemporary diagnosis using histology and genetics. Nat Rev Clin Oncol. 2009;6(11):627-637.
  3. Tefferi A, Thiele J, Vardiman JW. The 2008 World Health Organization classification system for myeloproliferative neoplasms: order out of chaos. Cancer. 2009;115(17):3842-3847.
Common Features of MF, PV, and ET

Three of the Ph(-) MPNs — MF, PV, and ET — share commonalities in the pathogenesis and symptomatology that may be related to dysregulated Janus kinase (JAK) signaling.1,2

The presentation of these conditions is variable, but MF, PV, and ET have many commonalities:

References
  1. Ghoreschi K, Laurence A, O'Shea JJ. Janus kinases in immune cell signaling. Immunol Rev. 2009;228(1):273-287.
  2. Delhommeau F, Jeziorowska D, Marzac C, et al. Molecular aspects of myeloproliferative neoplasms. Int J Hematol. 2010;91(2):165-173.
  3. Vardiman JW, Thiele J, Arber DA, et al. The 2008 revision of the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia: rationale and important changes. Blood. 2009;114(5):937-951.
  4. Thoennissen NH, Krug UO, Lee DHT, et al. Prevalence and prognostic impact of allelic imbalances associated with leukemic transformation of Philadelphia chromosome–negative myeloproliferative neoplasms. Blood. 2010;115(14):2882-2890.
  5. Schafer AI. Molecular basis of the diagnosis and treatment of polycythemia vera and essential thrombocythemia. Blood. 2006;107(11):4214-4222.
  6. The Leukemia & Lymphoma Society ® Web site. Essential thrombocythemia facts. Revised June 2012. http://www.lls.org/content/nationalcontent/resourcecenter/freeeducationmaterials/mpd/pdf/essentialprimarythrombocythemia.pdf. Accessed September 12, 2012.
  7. Mesa RA, Niblack J, Wadleigh M, et al. The burden of fatigue and quality of life in myeloproliferative disorders (MPDs): an international Internet-based survey of 1179 MPD patients. Cancer. 2007;109(1):68-76.
  8. Tefferi A, Barosi G, Mesa RA, et al. International Working Group (IWG) consensus criteria for treatment response in myelofibrosis with myeloid metaplasia, for the IWG for Myelofibrosis Research and Treatment (IWG-MRT). Blood. 2006;108:1497-1503.
  9. The Leukemia & Lymphoma Society® Web site. Polycythemia vera facts. Revised June 2012. http://www.lls.org/content/nationalcontent/resourcecenter/freeeducationmaterials/mpd/pdf/polycythemiavera.pdf. Accessed September 12, 2012.
  10. Schnittger S, Bacher U, Haferlach C, et al. Detection of JAK2 exon 12 mutations in 15 patients with JAK2V617F negative polycythemia vera. Haematologica. 2009;94(3):414-418.
  11. Tefferi A. Novel mutations and their functional and clinical relevance in myeloproliferative neoplasms: JAK2, MPL, TET2, ASXL1, CBL, IDH and IKZF1. Leukemia. 2010;24(6):1128-1138.
  12. The Leukemia & Lymphoma Society® Web site. Myelofibrosis facts. Revised April 2012. http://www.lls.org/content/nationalcontent/resourcecenter/freeeducationmaterials/mpd/pdf/idiopathicmyelofibrosis.pdf. Accessed September 10, 2012.
  13. Smith CA, Fan G. The saga of JAK2 mutations and translocations in hematologic disorders: pathogenesis, diagnostic and therapeutic prospects, and revised World Health Organization diagnostic criteria for myeloproliferative neoplasms. Hum Pathol. 2008;39:795-810.
  14. Mesa RA, Schwager S, Radia D, et al. The Myelofibrosis Symptom Assessment Form (MFSAF): an evidence-based brief inventory to measure quality of life and symptomatic response to treatment in myelofibrosis. Leuk Res. 2009;33(9):1199-1203.
References
  1. Cervantes F, Passamonti F, Barosi G. Life expectancy and prognostic factors in the classic BCR/ABL-negative myeloproliferative disorders. Leukemia. 2008;22:905-914.
  2. Tefferi A, Skoda R, Vardiman JW. Myeloproliferative neoplasms: contemporary diagnosis using histology and genetics. Nat Rev Clin Oncol. 2009;6(11):627-637.
  3. Tefferi A, Thiele J, Vardiman JW. The 2008 World Health Organization classification system for myeloproliferative neoplasms: order out of chaos. Cancer. 2009;115(17):3842-3847.
  4. National Comprehensive Cancer Network®. NCCN Clinical Practice Guidelines in Oncology™: myelodysplastic syndromes. 2010;V.2:1-35.
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