Polycythemia VeraPolycythemiaThrombocythemia, EssentialJanus Kinase 2Primary MyelofibrosisMyeloproliferative DisordersPipobromanThrombocytosisMinnesotaErythroid Precursor CellsAloeErythropoietinPhlebotomyHospitals, Group PracticeReceptors, ThrombopoietinErythropoiesisGranulocytesReceptors, ErythropoietinThrombosisHydroxyureaBloodlettingHematocritRetrospective StudiesMutation, MissenseHematopoiesis, ExtramedullaryMutationErythroid CellsAmino Acid SubstitutionGPI-Linked ProteinsPlatelet CountFollow-Up StudiesMegakaryocytesColony-Forming Units AssayBudd-Chiari SyndromeIsoantigensLeukemia, Myeloid, Chronic, Atypical, BCR-ABL NegativeChromosomes, Human, 19-20ThrombopoietinTreatment OutcomeBone MarrowHomozygoteHematopoietic Stem CellsSplenomegalyRisk Factors