Polycythemia vera, essential thrombocythemia, and primary myelofibrosis are genetically characterized by clonal mutations in JAK2, CALR, or MPL. The MPN diseases are thought to arise from a somatically mutated hematopoietic stem cell that gives rise to all myeloid cells, B cells, and natural killer cells [2]. This evidence concerns the gene JAK2 and acquired polycythemia vera.