In the present study, the results of using DNA from peripheral blood leukocytes showed that the frequency of the JAK2 mutation is comparable with other reports (Table 3). 22-28  Homozygous for the V617F mutation occurs in about 25% to 30% of patients with PV and PMF but is rare in patients with ET. 29-32  The use of ARMS-PCR showed that all patients with the JAK2V617F mutation were heterozygote. This evidence concerns the gene JAK2 and essential thrombocythemia.