Update on the impact of the JAK2 mutation on signalling pathways in myeloproliferative disorders.

In 2005, several groups discovered an acquired mutation affecting the gene for janus kinase 2 (JAK2 V617F) in a high proportion of patients with polycythaemia vera (PV), primary myelofibrosis (PMF) and essential thrombocythaemia (ET) (1–4). The discovery of this mutation represents a major breakthrough in molecular understanding of the myeloproliferative disorders (MPDs) that may have significant implications for diagnosis and treatment. This article will review the role of the JAKs and impact of the JAK2 mutation on the signalling pathways that underlie MPDs.