We report a case of prolonged extreme reactive thrombocytosis in a post-splenectomy patient with hereditary spherocytosis. A 29-year-old female patient presented with gall stones detected incidentally by abdominal ultrasonography. Her laboratory findings showed hemolytic anemia with spherocytosis on the peripheral blood smear and increased osmotic fragility. She was diagnosed with hereditary spherocytosis and underwent a laparoscopic cholecystectomy and splenectomy. After undergoing surgery, the hemolytic anemia was resolved but thrombocytosis was newly detected. Nineteen months after the splenectomy, the thrombocytosis was still persistent and extremely high. To our knowledge, this is the first report of a prolonged extreme reactive thrombocytosis after a splenectomy in Korea. (Korean J Hematol 2009;44:298-303.)

Keywords: Reactive thrombocytosis, Postsplenectomy, Hereditary spherocytosis