heterogenous group of bone marrow disorders characterized by uncontrolled proliferation of one or more cell lines

• leukocytosis
• thrombocytosis
• erythrocytosis
• myelofibrosis
• myeloproliferation
• splenomegaly

• one disease entity can evolve into another
• transformations are usually toward more malignant disorders
• these disorders are generally not curable (except CML)

• uncontrolled proliferation
• dysequilibrium
• dysharmony

• dx (usually idiopathic) 
  • more than 1 million platelets
  • abnormal morphology
  • qualitative defects- bleeding time, pit aggegation studies often normal
• tx- ASA, myelosuppressive therapy for high risk patients or more than 60 yrs old, hydroxyurea
• can evolve into:
  • PV
  • CML
  • AML
  • MFMM

• age > 60 yrs
• lower than normal Hb
• WBC more than 15 x 10^9/L

2 or more risk factors means worse survival

• plasma EPO is low
• blood/marrow form clonal CFU-E

• progenitor cells in p. vera ptients form erythroid colonies in vitro with no hematopoietic growth factors aka endogenous erythroid colonies
  • progenitors from normal adults will not form colonies without exogenous growth factors
  • endogenous erythroid colony assay can help with P. vera dx
• expanded blood volume
• increase RBC masss

disease of insidious onset and chronic course

• mutation in JAK2
  • cause PV like disease in mice
    • cauyse erythrocytosis, granulocytosis, but not thrombocytosis
    • bone marrow and spleen trilineage hyperplasia, fibrosis
  • transform cell lines
    • GF independece of factor dependent cell lines
    • EPO hypersensitivity