• Late age, chronic slow progression of scarring of bone marrow
• End result of PV, ET & other MPDs.
• JAK2 tyrosine kinase activation
• Increased marrow fibrosis due to PDGF & TGFβ from neoplastic stem cells & megakaryocytes. (fibroblasts are non neoplastic).
• Massive hepatosplenomegaly – extramedullary hemopoiesis.
• Abnormal RBC – anemia.
• Many Teardrop RBC*
• Infections / bleeding – terminal
• Transformation to AML - rare