Myelofibrosis is characterized by bone marrow fibrosis, symptom burden, splenomegaly, and cytopenias

Myelofibrosis is a Philadelphia chromosome–negative myeloproliferative neoplasm (MPN)1 characterized by bone marrow fibrosis, symptom burden, splenomegaly, and cytopenias.2 Myelofibrosis is a disease with significant heterogeneity in natural history and symptom burden. Patients with myelofibrosis fall along a spectrum that ranges from those who are essentially asymptomatic to those who have severe symptoms that affect daily functioning and quality of life.3-5 Myelofibrosis can be a primary disease or it can be secondary to other conditions, including malignancies and other hematologic diseases.6

Although the precise etiology of myelofibrosis remains unknown, overactive Janus-associated kinase (JAK) pathway signaling is present in all patients with the disease.7,8 Multiple mechanisms, including genetic mutations,9-11 excessive production of cytokines,12 increased JAK1 signaling,13 and damaged intracellular signaling14 may play a role in overactive JAK pathway signaling.

Because myelofibrosis has a heterogeneous presentation, determining a patient’s prognosis can be difficult.15 However, progress in understanding the clinical variables associated with myelofibrosis has led to the development of prognostic scoring systems, including the International Prognostic Scoring System (IPSS). The IPSS estimates prognosis based on risk factors present at diagnosis.16

Prevalence and demographics

Myelofibrosis is a rare disease, with a prevalence of 16,000 to 18,500 patients in the United States.17 Although myelofibrosis can occur at any age, the median age at diagnosis ranges from 60 to 67 years.2,3 The disease affects both men and women.18

image of myelofibrosis patient Eleanor

Eleanor is a retired elementary school teacher who presents with fatigue and night sweats.



1. Vannucchi AM, Guglielmelli P, Tefferi A. CA Cancer J Clin. 2009;59:171-191. 2. Abdel-Wahab OI, Levine RL. Annu Rev Med. 2009;60:233-245. 3. Mesa RA, Niblack J, Wadleigh M, et al. Cancer. 2007;109:68-76. 4. Emanuel RM, Dueck AC, Geyer HL, et al. J Clin Oncol. 2012:30:4098-4104. 5. Geyer HL, Scherber RM, Dueck AC, et al. Blood. 2014;123(24):3803-3810. 6. The Merck Manual for Health Care Professionals. Available at: Accessed March 3, 2013. 7. Verstovsek S. Clin Cancer Res. 2010;16:1988-1996. 8. Jones AV, Campbell PJ, Beer PA, et al. Blood. 2010;115:4517-4523. 9. Pikman Y, Lee BH, Mercher T, et al. PLoS Med. 2006;3:1140-1151. 10. Kralovics R, Passamonti F, Buser AS, et al. N Engl J Med. 2005;352:1779-1790. 11. Kralovics R. Leukemia. 2008;22:1841-1848. 12. Tefferi A, Vaidya R, Caramazza D, Finke C, Lasho T, Pardanani A. J Clin Oncol. 2011;29:1356-1363. 13. Quintás-Cardama A, Vaddi K, Liu P, et al. Blood. 2010;115:3109-3117. 14. Fourouclas N, Li J, Gilby DC, et al. Haematologica. 2008;93:1635-1644. 15. Passamonti F, Cervantes F, Vannucchi AM, et al. Blood. 2010;115:1703-1708. 16. Cervantes F, Dupriez B, Pereira A, et al. Blood. 2009;113:2895-2901. 17. Data on file. Incyte Corporation. 18. The Leukemia & Lymphoma Society. White Plains, NY; 2012. Number 14.

By: World Health Organization (WHO)
A diagnostic worksheet from the WHO for primary MF, PV, and ET.
By: International Working Group for Myeloproliferative Neoplasms Research and Treatment (IWG-MRT)
Diagnostic criteria from the IWG-MRT.