Introduction Neoplasia of mature myeloid cells (mostly megakaryocytes) typically high levels of erythrocytes, granulocytes are also seen Caused by a JAK2 kinase mutation Seen mainly in older adults (5th-6th decade) Presentation Symptoms bleeding Prognosis, Prevention, and Complications May progress to acute leukemia or myelofibrosis High risk of venous thrombosis also increased risk of bleeding due to dysfunction of neoplastic platelets