Infrequent occurrence of this unique JAK2 mutation has been reported in chronic myelomonocytic leukemia (CMML), atypical or unclassified myeloproliferative disorder (MPD), myelodysplastic syndrome (MDS), systemic mastocytosis (SM), and chronic neutrophilic leukemia (CNL) [10–16]. This evidence concerns the gene JAK2 and chronic neutrophilic leukemia.