Myelofibrosis

Introduction

• Neoplasia of mature myeloid cells
  • most notably megakaryocytes
• Most commonly seen in older adults (5th/6th decade)
• Result of a JAK2 kinase mutation 
• Megakaryocyte hyperplasia results in fibrotic obliteration of the bone marrow
• result of increased production of PDGF

Presentation

• Symptoms
  • splenomegaly 
    • secondary to extramedullary hematopoiesis
  • bleeding
    • megakaryocytes are dysfunctional
  • thrombosis
• platelets can rupture which stimulates coagulation cascade

Evaluation

• Peripheral blood smear
  • tear-drop RBC  
    • membrane is disrupted when RBC passed through fibrosis to leave bone marrow
  • nucleated RBCs
  • band granulocytes