Polycythaemia vera — Rapid | Doctor’s Passport

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.
Confirm with integrated haemoglobin or haematocrit, JAK2 mutation, low erythropoietin and panmyelotic marrow findings; iron deficiency can mask the true erythrocytosis.
First-line thrombosis prevention is venesection to keep haematocrit below 0.45 plus low-dose aspirin when there is no contraindication.
Age over 60 years or previous thrombosis usually defines high thrombotic risk and adds cytoreduction, commonly hydroxycarbamide or interferon according to reproductive and toxicity considerations.
An acute splanchnic thrombosis should trigger myeloproliferative testing even when counts are normal because haemodilution, iron deficiency or hypersplenism can mask PV.
Avoid routine iron replacement: treat proven symptomatic deficiency only with specialist supervision and frequent haematocrit monitoring.

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.

Major bleeding with extreme thrombocytosis may reflect acquired von Willebrand syndrome and requires urgent haemostasis testing and cytoreductive planning.

Rapid anaemia, leucoerythroblastic film, enlarging spleen, weight loss, fever or blasts suggests post-PV myelofibrosis or AML transformation.

Thrombotic presentation

Arterial events and DVT or PE occur, while portal, hepatic or cerebral venous thrombosis is especially suggestive.

Progression pattern

New anaemia, teardrops, nucleated red cells, blasts, splenic pain or systemic symptoms suggests fibrotic or leukaemic evolution.

Investigation priorities

First-line erythrocytosis assessmentFirst stepFirst line

Confirm persistence and identify relative, hypoxic, renal, hormonal and clonal clues.

First-line molecular test: JAK2 V617FFirst line

Identify the principal clonal driver in suspected PV and unusual-site thrombosis.

Management branches

Sustained erythrocytosisSeparate clone from hypoxia and volume

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.
Use exon 12, marrow and directed secondary or hereditary testing when the initial pattern does not resolve the diagnosis.

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.Assess hydration, blood pressure and cardiovascular tolerance. Monitor ferritin and symptoms but do not replace iron routinely; adjust volume and frequency in pregnancy, frailty or cardiac disease.

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.Review gastrointestinal bleeding, anticoagulation and extreme thrombocytosis. Use gastric protection when indicated and do not substitute aspirin for anticoagulation after venous thrombosis.

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