Advances in the understanding and management of myeloproliferative disorders.

Myeloproliferative disorders (MPDs) comprise a group of bone marrow diseases, characterised by abnormal or excessive cell production. The four original classifications of MPD include chronic myeloid leukaemia (CML), polycythaemia vera (PV), essential thrombocythaemia (ET), and primary myelofibrosis (PMF). Among these disorders, CML can now be differentiated by the presence of the Philadelphia (Ph)-positive abnormality and its specific molecular marker (disrupted protein kinase breakpoint cluster region ⁄Abelson murine leukaemia (BCR ⁄ABL)). Knowledge of the molecular basis of the Ph-negative MPDs (PV, ET and PMF) has until recently been very limited. However, this has recently changed following the discovery of the janus kinase 2 (JAK2 V617F) mutation in a significant proportion of patients with Ph-negative MPDs (1–4). In this article, the key developments in molecular understanding of the MPDs will be reviewed.