JAK2 and vasculitis: Herein, we report a case of <i>Janus Kinase2 (JAK2)</i> V617F mutation-positive essential thrombocythemia (ET) associated with vasculitis.<h4>Case presentation</h4>A 60-year-old man with <i>JAK2</i> V617F mutation-positive ET underwent coronary artery bypass grafting after recurrent myocardial infarctions and coronary stent occlusions.