↑Hct, pruritus after shower, thrombosis, splenomegaly
Confirm: JAK2 mutation (95%) + ↓EPO
Treat: Phlebotomy to Hct <45% + low-dose aspirin; cytoreduction if high-risk (age >60 / prior thrombosis): hydroxyurea or ropeginterferon alfa-2b (first-line option, esp. younger patients; pegylated interferon preferred in pregnancy/young women); ruxolitinib for hydroxyurea-resistant/intolerant PV or refractory pruritus (RESPONSE)
Order set
- FBC
- JAK2 mutation
- EPO level
- Ferritin, urate
Criteria
AdmitThrombosis, bleeding, or symptomatic hyperviscosity
DischargeVenesected to target Hct, aspirin ± cytoreduction, follow-up
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Thrombosis
- Bleeding
- Marked splenomegaly
Differentials
- Secondary polycythaemia (hypoxia)
- Relative (dehydration)
- Other MPN
Common mistakes
- Missing secondary cause
- Not addressing thrombotic risk
Disposition & follow-up
Venesection + aspirin; cytoreduction if high-risk.
Discharge package
MedicationsAspirin ± cytoreduction; venesection
Follow-upHaematology; Hct monitoring
Warning symptomsThrombosis symptoms, bleeding, headache
💊 Treatment detail — doses & preparation
Venesectiondefinitive
Dose450 mL weekly to haematocrit <0.45
PreparationLarge-bore needle
MonitorHaematocrit after each; target <0.45
Aspirinantiplatelet
DosePV: 75 mg OD (all patients)
Preparation75 mg enteric-coated tablets
MonitorBleeding, dyspepsia; avoid in viral illness in children
Hydroxycarbamideantimetabolite
DosePV/sickle cell: 15–20 mg/kg OD titrated to counts
Preparation500 mg capsules
MonitorFBC 2–4 wkly during titration; leg ulcers, skin cancer risk long-term
📖 BSH / ELN MPNReviewed July 2026