1. Inclusion Pediatric and adult patients with suspected congenital primary and secondary erythrocytosis Patients < 20 years with polycythemia vera Exclusion Patients with secondary erythrocytosis due to a known cardiac, pulmonary, or renal disease Observational patients Patients with secondary erythrocytosis due to an underlying disorder (e.g. renal disorder, Epo- producing tumor) which has been identified during the diagnostic work-up of apparent idiopathic erythrocytosis

2. Before the inclusion of a patient with suspected congenital erythrocytosis or PV in childhood and adolescence into the register exclude causes for relative or apparent erythrocytosis (e.g. dehydration, Smoker‘s polycythemia) confirm the presence of absolute erythrocytosis in an independent analysis exclude obvious cardiac and pulmonary causes of secondary erythrocytoses (e.g. COPD, cyanotic cardiac defects) in patients older than 20 years, exclude polycythemia vera according to established diagnostic criteria (PVSG and/or WHO)

3. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

4. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

5. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

6. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

7. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

8. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

9. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

10. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

11. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly

12. Serum erythropoietin  (or upper normal range) Serum erythropoietin  (or lower normal range) PRV-1mRNA expression nl.; ØEEC ; JAK2 V617F - PRV-1mRNA expression  ; EEC  ; JAK2 V617F + Polycythemia vera  BM biopsy & cytogenetics Sequencing of EPOR gene exon 7+8  Epo sensitivity assay “+”  PFCP “-”  PFCP ?   BM biopsy Hemoglobin oxygen affinity nl.Hemoglobin oxygen affinity  VHL gene analysis Hemoglobin analysis nlAbnormal hemoglobin Globin gene analysis Chuvash P./other VHL mutation? further endocrinol. & nephrol. diagnostics (e.g. angiography) Exclusion of Epo-producing tumour ( CNS-MRI, sonography) 2,3-BPG quantification 2,3-BPG deficiency ? 2,3-BPG mutase  ? Hereditary PK abnormality ? hemoglobin variant with hyperaffinity to O 2 Diagnostic algorithm for absolute erythrocytoses PHD2 gene analysis (& other g.) Red cell mass  (> mean + 25%) or hemoglobin or hematocrit  (> mean + 2 SD) SaO 2 >92 %SaO 2 <92 %Cardiac or pulmonary disorder?  leukocytosis  thrombocytosis  splenomegaly Polycythemia vera ?  PRV-1, EEC, JAK2, BM Isolated erythrocytosis, no significant splenomegaly