 "JAK2" orthologs  have been identified in all mammals for which complete genome data are available.JAK2 gene fusions with the TEL(ETV6) (TEL-JAK2) and PCM1 genes have been found in patients suffering leukemia, particularly clonal eosinophilia forms of the disease.Mutations in JAK2 have been implicated in polycythemia vera, essential thrombocythemia, and myelofibrosis as well as other myeloproliferative disorders.