For patients with essential thrombocythemia who develop venous thrombosis in the setting of elevated platelet counts, would you continue lifelong anticoagulation even after cytoreduction is achieved?

This is a fantastic question, a true real-life scenario, with unfortunately little data to drive clinical decision making. What we do have to work with is that the combination of ASA plus anticoagulation increases the risk of bleeding, but does not decrease the risk of recurrent thrombosis in MPNs. Therefore in a case like this I would do one or the other. If this was a provoked low-risk clot, and the patient completed at least 3-6 months of anticoagulation, and there is resolution of the clot at the end of the course of anticoagulation, there would be an opportunity to discontinue anticoagulation and resume ASA. For any patient (MPN or not) who has an unprovoked DVT, the risk of recurrence is 10% in the first year, and 5% annually thereaft...

My first instinct upon reading this question is to express my suspicion that any ET patient who has a venous thrombosis may actually have polycythemia vera (PV), regardless of the height of the platelet count. My reasons for being suspicious are many. First, there is no correlation in true ET between the platelet count and venous thrombosis. On the contrary, in true ET, there is a correlation with very high platelet counts (> 900,000/mL) and hemorrhage, though rarely spontaneous, due to acquired von Willebrand disease. Second, PV is not just erythrocytosis, it is a panmyelopathy, involving red cells, white cells and platelets and only rarely presents with erythrocytosis alone. Even more important, is the fact that in PV, particularly in wom...