ET patients carrying a JAK2 V617F mutation had higher peripheral blood WBC counts (P = 0.001), higher Hb concentrations (P = 0.001), and lower PLT counts (P = 0.037) and were more prone to splenomegaly and abnormal endogenous coagulation (P < 0.05). This evidence concerns the gene GSTM1 and Splenomegaly.