Phagocytosed platelets in leukocytes from patients with PV or ET with or without a history of thrombosis. The presence of leukocytes with intracellular platelets was assessed as described in “Flow cytometry.” Symbols represent the percentage of neutrophils (A) or monocytes (B) with intracellular platelet antigens. Grey triangles indicate patients with a single thrombotic episode. Black circles indicate patients with 2 thrombotic episodes (n = 5 of 21). Horizontal lines indicate mean values.