The median time between the initiation of anagrelide therapy and event onset in patients with thrombosis events was 241.5 days, and values at the time of onset were as follows: median WBC count, 11.5 × 109/L; median neutrophil rate, 81.2%; median Hb level, 13.0 g/dL; and median platelet count, 709 × 109/L. The gene discussed is GSTM1; the disease is Venous thrombosis.