Myelofibrosis, JAK2 inhibitors and erythropoiesis

The term myeloproliferative disorders was introduced by William Dameshek1 in 1951 to describe four different diseases with a related pathogenesis: polycythaemia vera (PV), essential thrombocythaemia (ET), primary myelofibrosis (PMF) and chronic myeloid leukaemia. The discovery of the Philadelphia chromosome and the fusion gene BCR-ABL has permitted the definition of chronic myeloid leukaemia as a specific entity. The pathogenesis of the other non-BCR-ABL myeloproliferative disorders, now called myeloproliferative neoplasms (MPNs),2 remained elusive until 2005. At that time, these disorders were considered orphan disorders and were not the subject of intensive clinical interest. Nevertheless, it was clear that PV, ET and PMF had closely related pathogeneses, with some clinical, histological and biological features in common. This was underscored by the progression of some ETs to PVs, and some ETs or PVs to myelofibrosis, respectively called post-ET or post-PV myelofibrosis.