PassFinals
Haematology & Oncology

Polycythaemia Vera

A clonal myeloproliferative disorder, usually driven by a JAK2 mutation that makes marrow precursors hypersensitive to growth signals, so red cells (and often white cells and platelets) are overproduced independent of erythropoietin, raising blood viscosity and thrombosis risk while erythropoietin itself is suppressed.

In a nutshell

PV is a clonal erythrocytosis, usually JAK2-associated, with risk driven mainly by thrombosis and haematocrit. Confirm the cause, keep haematocrit below 0.45, use carefully selected antiplatelet/cytoreductive treatment and monitor for transformation.

Classic presentation

Persistent erythrocytosis with headache, pruritus after bathing, erythromelalgia, thrombosis or an incidental raised FBC.

Key points

  • Exclude relative and secondary erythrocytosis.
  • JAK2 testing supports the diagnosis; marrow assessment may be needed.
  • The central treatment target is haematocrit below 0.45.
  • Aspirin is not automatic when bleeding risk or acquired von Willebrand syndrome is present.
  • Ruxolitinib is a NICE-defined option after hydroxycarbamide resistance or intolerance.

First-line investigation

Repeat FBC, assess oxygenation/secondary causes and arrange JAK2 and specialist marrow assessment.

Management

Confirm PV and risk

  • Confirm clonal erythrocytosis, exclude secondary causes, assess thrombosis/bleeding risk and document JAK2 and marrow findings through haematology.1,2

Control haematocrit and vascular risk

  • Use specialist-directed venesection to maintain haematocrit below 0.45 and individualise antiplatelet treatment after assessing bleeding risk and contraindications.1,3,4

Add cytoreduction when indicated

  • Use cytoreduction for high-risk disease, significant symptoms, intolerance of venesection or inadequate control; select hydroxycarbamide or interferon-based approaches with specialist input.1,3,4

Escalate resistant or intolerant disease

  • Consider ruxolitinib only within the current NICE PV criteria after hydroxycarbamide resistance or intolerance, not as routine first-line treatment.5,4

Monitor transformation and symptoms

  • Review FBC, iron status, symptoms, thrombosis/bleeding, treatment toxicity and progression to MF, MDS or AML.1,3,2

Exam traps

  • A raised red-cell count from dehydration or hypoxia is not PV.
  • PV can also raise platelets and white cells.
  • Thrombosis and bleeding can both occur.
  • Do not start cytoreduction or ruxolitinib without risk and specialist assessment.

Illustrations

JAK2-STAT constitutive activationDiagram of the JAK2-STAT signalling pathway showing constitutive activation driving erythropoietin-independent marrow proliferation.PassFinals · original
Erythropoietin in primary versus secondary polycythaemiaDiagram contrasting suppressed erythropoietin in primary (marrow-driven) polycythaemia with raised erythropoietin in secondary (hypoxia- or tumour-driven) polycythaemia.PassFinals · original

Key sources

  1. BSH: Diagnosis and management of polycythaemia vera (UK BSH diagnostic, risk-stratification and management guidance for PV.)Published 27 Nov 2018
  2. NHS: Erythrocytosis (UK patient information on primary and secondary erythrocytosis/PV and thrombosis symptoms.)
  3. BSH: Management of specific situations in polycythaemia vera and secondary erythrocytosis (UK BSH guidance for PV-specific situations and secondary erythrocytosis.)Published 13 Nov 2018
  4. BNF online (Check current antiplatelet, cytoreductive, JAK-inhibitor and supportive prescribing.)
  5. NICE TA921: Ruxolitinib for treating polycythaemia vera (NICE appraisal of ruxolitinib for adults with PV who are resistant to or intolerant of hydroxycarbamide.)Published 9 Aug 2023

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.