JAK2 V617F mutation occurs at one allele (the heterozygous pattern) or both alleles (the homozygous pattern) in PV patients, and previous studies have reported that the JAK2 V617F homozygous group presents higher hemoglobin concentration, higher incidence of myelofibrotic change than the JAK2 V617F heterozygous group. This evidence concerns the gene JAK2 and acquired polycythemia vera.