A 55-year-old man has splenomegaly, pruritus after bathing (aquagenic), plethora, and Hb 19.5 g/dL, haematocrit 62%. JAK2 V617F mutation is positive. Serum erythropoietin is low. The diagnostic condition is polycythaemia vera (PV). The MOST important initial therapy to prevent thrombosis is:

• A Iron supplementation
• B Phlebotomy to maintain haematocrit < 45% plus low-dose aspirin ✓
• C High-dose hydroxyurea alone
• D Ruxolitinib as first-line cytoreduction

Explanation

The CYTO-PV trial established that maintaining haematocrit < 45% in PV men (< 42% in women) significantly reduces the rate of cardiovascular death and major thrombosis compared to lenient targets (45–50%). Phlebotomy is the cornerstone to achieve this, combined with low-dose aspirin (81–100 mg/day) to reduce thrombotic risk. Hydroxyurea is added for high-risk patients (age >60 or prior thrombosis). Ruxolitinib (JAK1/2 inhibitor) is second-line for hydroxyurea failure or intolerance.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.