Keywords: Erythrocytosis


Appropriate Tests


Polycythaemia can be relative (decreased plasma volume) or true polycythaemia. True polycythaemia can be primary (the myeloproliferative neoplasm Polycythaemia vera) or secondary (to states associated with appropriate or abnormal excessive erythropoietin.

Review clinical findings, including history of smoking and diuretic therapy.

Follow up Full blood count, Blood film, Erythropoietin.

Relative polycythaemia

The increased Hb / Haematocrit elevation is due to reduced plasma volume, eg, dehydration, diuretic therapy.


Stress polycythaemia (spurious polycythaemia)

Gaisböck syndrome, associated with smoking and alcohol use.


True polycythaemia

Erythropoietin (Epo) level may be useful: increased levels in secondary erythrocytosis, low to undetectable levels in Polycythaemia vera. Mutational analysis, ie, Jak-2 mutation can also be useful if present (in a proportion of Polycythaemia vera cases).

Chronic hypoxaemia

Blood gas arterial / Haemoximetry. See also Cyanosis.

  • Heavy smoking

See Smoking

  • Cyanotic congenital heart disease
  • Chronic respiratory disease


Renal disorders


  • Polycystic kidney disease

See Cystic renal disease

  • Renal artery stenosis

See under Hypertension.

  • Renal cell carcinoma

See under Renal mass.

  • Hydronephrosis

See under Urinary tract obstruction.



  • Uterine leiomyoma


  • Hepatocellular carcinoma


  • Cerebellar haemangioblastoma


Primary haematological disorder


High affinity haemoglobin

Haemoglobin oxygen affinity, Haemoglobin electrophoresis; Haemoglobin M; Pulse oximetry.

Polycythaemia vera

Review Full blood count, Blood film, Epo level, Jak-2 (and other relevant) mutations. Bone marrow aspiration and trephine biopsy may sometimes be useful in documenting other features of a myeloproliferative neoplasm (cytogenetic studies may show a clonal abnormality but there is not a single recurring abnormality characteristic of Polycythaemia vera).

Presence in vitro of the formation of spontaneous erythroid colonies (SECs) in the absence of Epo is a sensitive but not specific finding in Polycythaemia vera, and of limited availability.

A lower than normal range Epo level is of high diagnostic specificity for Polycythaemia vera.

Positivity for JAK-2 mutation confirms the presence of a myeloproliferative neoplasm but is not specific for Polycythaemia vera.

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