Patients with or without cytoreduction did not differ in the rate of PV, essential thrombocythaemia or MF diagnosis, age >60 years, BCS as index event, Hb >15 g/dl, WBC count >14 × 109/l, platelet count >500 × 109/l, splenomegaly and VKA treatment (data not shown). The gene discussed is GSTM1; the disease is Splenomegaly.