Question category: Haematology
A 50 year old gentleman presents with pruritus. This is most marked after a hot shower. He is also having intermittent headaches and dizziness. Over the last few days he has noticed swelling of his left calf. Bloods reveal a raised haemoglobin, increased packed cell volume and mildly elevated platelets and white cells. JAK2 mutational analysis is positive. Which of the following is the most appropriate treatment?