A 32-year old male with unremarkable past clinical history presents with persistent thrombocytosis (Hb = 15.6 g/dL; Hct = 46.1%; WBC = 6.76 × 109/L; Plt = 745 × 109/L; Epo and LDH levels within normal ranges). This evidence concerns the gene GSTM1 and thrombocytosis disease.