87 Primary Myelofibrosis (PMF)

Michelle To and Valentin Villatoro

Affected Cell Line: Granulocytes and Megakaryocytes in the bone marrow resulting in secondary fibroblast stimulation and fibrotic desposition in the bone marrow.1,2


Mutation: JAK 2 V617F, CALR, and MPL gene mutations.1,3


Age Group Affected: >50 years old, occurs equally between males and females.4



Primary myelofibrosis is characterized by two stages:

1. Prefibrotic Stage

The bone marrow is hypercellular and shows minimal reticulin and fibrosis initially, with an increase in megakaryocytes and granulocytes.1


2. Fibrotic Stage

Peripheral blood shows a characteristic leukoerythroblastic picture (immature granulocyte and erythrocyte precursors) with poikilocytosis, especially teardrop cells and elliptocytes.1


Bone marrows shows marked fibrosis.1 Extramedullary hematopoiesis is often seen, with cells accumulating in the spleen, liver, and other organs. 


Laboratory Findings for Primary Myelofibrosis:2,4,5


Early Stage:

RBC: Normal

WBC: Increased

PLT: Increased

Hb: Normal


Fibrotic Stage:

RBC: Decreased


PLT: Decreased

Hb: Decreased


Platelets have a dysplastic morphology (Giant, agranular)

May see micromegakaryocytes

Variable poikilocytosis


Fibrotic Stage:


Leukoerythroblastic picture

Teardrop cells




Often results in a dry tap


Fibrosis of varying degrees (Marked fibrosis in later stages)

Megakaryocyte aggregates



Other Tests:

PLT Function: Abnormal


1. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al. editors. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues Volume 2. 4th ed. International Agency for Research on Cancer (IARC); 2008.

2. Schaub CR. Chronic Myeloproliferative disorders I: chronic myelogenous leukemia. In: Clinical hematology and fundamentals of hemostasis. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 371-84.

3. Choi CW, Bang S-M, Jang S, Jung CW, Kim H-J, Kim HY, et al. Guidelines for the management of myeloproliferative neoplasms. Korean J Intern Med [Internet]. 2015 Nov 30 [cited 2018 Jul 9];30(6):771–88. Available from: http://kjim.org/journal/view.php?doi=10.3904/kjim.2015.30.6.771
4. Randolph TR. Myeloproliferative neoplasms. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 450-78.

5. Randolph TR. Myeloproliferative neoplasms. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p.561-90.


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Primary Myelofibrosis (PMF) Copyright © 2019 by Michelle To and Valentin Villatoro is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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