Myelofibrosis (MF) is a myeloproliferative neoplastic disorder. MF is characterized by bone marrow fibrosis, splenomegaly and/or hepatomegaly, and constitutional symptoms.1

Incidence and Prevalence of Myelofibrosis

Based on a meta-analysis of 34 highly heterogeneous studies conducted across the globe, the worldwide annual incidence rate of MF is reported to be around 0.47 cases per 100,000 people.2 Depending on geographic location, incidence rates of MF vary widely.

According to Orphanet, the prevalence of MF ranges from 1 to 9 in every 100,000 people.3 

Studies reporting the prevalence of MF are very rare. The large variations in reported incidence and prevalence across the globe stem from a lack of uniformity in the definition of MF as well as coding differences added to limiting factors (bias, incomplete data, problems with assessing statistical significance) influencing registry data collection.4 

Read more about MF diagnosis

Geographical Factors of MF

According to a study analyzing trends in the US Surveillance, Epidemiology, and End Results (SEER) data from 2002 to 2016, the incidence rate of primary MF was 0.44 per 100,000 person-years.5 Other sources estimate MF incidence to be 1.5 cases per 100,000 people in the United States.6 

Although trends indicate improved survival over time, patients with primary MF in the United States demonstrate a 5-year mortality rate of 51% with a short median survival time of 5.2 to 5.9 years.5

The incidence of MF in Northern Europe is around 0.5 cases per 100,000 person-years,6 ranging from 0.1 to 1 case per 100,000 people per year.7

The incidence rate of primary MF in Sweden is around 0.52 per 100,000 person-years.8 

Read more about MF prognosis

Age Factors of MF

While MF can occur at any age, it commonly affects individuals over 50 years of age, with the median age of diagnosis being around 65 years.6 When primary MF affects children, it usually occurs before the age of 3 years.6

Sex Factors of MF

In adults, MF affects men and women equally. However, when MF occurs in younger children, girls are affected 2 times more frequently than boys.6

Race/Ethnicity Factors of MF

An increased prevalence of MF has been reported among Ashkenazi Jews.3

In a study conducted at the University of Illinois between 1990 and 2012, White patients with polycythemia vera and essential thrombocythemia demonstrated a higher likelihood of progression to secondary MF than Nonwhite patients.9

Read more about MF comorbidities

Epidemiology of Myelofibrosis Subtypes

While White patients are more likely to develop secondary MF, patients with primary MF (subdivided into prefibrotic and overtly fibrotic types) also demonstrate specific trends. 

A study reported trends in 683 patients with a diagnosis of primary MF. Those who developed the prefibrotic type (n=132) were predominantly female and younger with higher platelet and hemoglobin counts, lower white blood cell counts, a smaller spleen index, and a higher incidence of splanchnic vein thrombosis. Overall, patients with the prefibrotic primary MF type exhibited a more indolent phenotype with very long survival compared with those who had the overtly fibrotic primary MF type. This highlighted the importance of the effects of age and sex on primary MF phenotype as well as potential disease-related complications and survival outcomes.10

Read more about MF types


  1. Primary myelofibrosis. MedlinePlus. Updated September 1, 2014. Accessed December 13, 2022.
  2. Titmarsh GJ, Duncombe AS, McMullin MF, et al. How common are myeloproliferative neoplasms? A systematic review and meta-analysis. Am J Hematol. 2014;89(6):581-587. doi:10.1002/ajh.23690
  3. Primary myelofibrosis. Orphanet. Updated May 2019. Accessed December 13, 2022.
  4. Moulard O, Mehta J, Olivares R, Iqbal U, Mesa RA. Epidemiology of myelofibrosis (MF), polycythemia vera (PV) and essential thrombocythemia (ET) in the European Union (EU). Blood. 2012;120(21):1744. doi:10.1182/blood.V120.21.1744.1744
  5. Verstovsek S, Yu J, Scherber RM, et al. Changes in the incidence and overall survival of patients with myeloproliferative neoplasms between 2002 and 2016 in the United States. Leuk Lymphoma. 2022;63(3):694-702. doi:10.1080/10428194.2021.1992756
  6. Primary myelofibrosis. National Organization for Rare Disorders (NORD). Accessed December 13, 2022.
  7. Moulard O, Mehta J, Fryzek J, Olivares R, Iqbal U, Mesa RA. Epidemiology of myelofibrosis, essential thrombocythemia, and polycythemia vera in the European Union. Eur J Haematol. 2014;92(4):289-297. doi:10.1111/ejh.12256
  8. Hultcrantz M, Landtblom AR, Andréasson B, et al. Incidence of myeloproliferative neoplasms – trends by subgroup and age in a population-based study in Sweden. J Intern Med. 2020;287(4):448-454. doi:10.1111/joim.13019
  9. Khan I, Shergill A, Saraf SL, et al. Outcome disparities in Caucasian and non-Caucasian patients with myeloproliferative neoplasms. Clin Lymphoma Myeloma Leuk. 2016;16(6):350-357. doi:10.1016/j.clml.2016.02.036
  10. Barosi G, Rosti V, Bonetti E, et al. Evidence that prefibrotic myelofibrosis is aligned along a clinical and biological continuum featuring primary myelofibrosis. PLoS One. 2012;7(4):e35631. doi:10.1371/journal.pone.0035631

Reviewed by Hasan Avcu, MD, on 12/23/2022.