Abstract: To the Editor:Essential thrombocythemia (ET) complicated by cerebral venous sinus thrombosis (CVST) is exceptionally rare.Hitherto,few studies have mentioned the role of Janus kinase 2V617F (JAK2V617F) mutation in ET patients who developed CVST;thus,the strategy and long-term outcomes are yet rarely reported.The present study documented four cases,wherein CVST was the first manifestation ofJAK2V617F-positive ET.