Synopsis
Distinguish clonal panmyelosis from relative and secondary erythrocytosis, prevent thrombosis with haematocrit control and recognise bleeding, progression and pregnancy-specific risks.
- Suspect PV with sustained erythrocytosis plus leucocytosis, thrombocytosis, splenomegaly, aquagenic pruritus, erythromelalgia or unusual-site thrombosis.
- First-line assessment is repeat FBC and film, oxygen saturation, smoking and medicine review, ferritin, renal and liver tests, serum erythropoietin and JAK2 V617F testing.
- If JAK2 V617F is negative but PV remains likely, test JAK2 exon 12 and perform marrow and secondary or hereditary erythrocytosis assessment through haematology.
Key red flags
Focal neurology, chest pain, painful swollen limb, abdominal pain with portal or hepatic-vein thrombosis, or visual loss requires immediate vascular assessment and treatment.
Arterial events and DVT or PE occur, while portal, hepatic or cerebral venous thrombosis is especially suggestive.
Investigation priorities
Confirm persistence and identify relative, hypoxic, renal, hormonal and clonal clues.
Identify the principal clonal driver in suspected PV and unusual-site thrombosis.
Management branches
Haemoglobin or haematocrit remains elevated on repeat testing.
- Assess volume, smoking, oxygen, sleep, medicines, renal and liver disease, thrombosis, pruritus and spleen.
- Measure erythropoietin and JAK2 V617F with ferritin and organ baseline.
Key medicines
VenesectionRemove approximately 450 mL of blood per session in a typical adult, using smaller volumes for low body mass or cardiovascular disease, and repeat at a clinically safe interval until haematocrit is below 0.45, then maintain that target.
Low-dose aspirinGive 75 mg orally once daily long term when there is no active bleeding, major aspirin intolerance or acquired von Willebrand syndrome that makes antiplatelet therapy unsafe.