polycythemia rubra vera complicationspolycythemia rubra vera diagnosispolycythemia rubra vera prognosispolycythemia vera complicationsrubra verasecondary polycythemia verapolycythemia vera myelofibrosispolycythemia vera prognosispolycythemia vera will result indefine polycythemia veraprimary polycythemia verapolycythemia vera natural treatment