Myeloproliferative neoplasms (MPNs) are a group of clonal disorders leading to the excessive production of mature blood cells. The type of MPN is determined by the type of blood cell which is being overproduced. The three main types of MPNs are polycythemia vera (PV), essential thrombocythemia (ET) and myelofibrosis (MF). Other rarer types include chronic neutrophilic leukemia, chronic eosinophilic leukemia and mastocytosis. Chronic myelomonocytic leukemia (CMML) shows symptoms of MPN and myelodysplastic syndromes (MDS), so it classed as an overlap disorder. Some classify chronic myeloid leukemia (CML) as an MPN, but it is generally more common to treat it separately.
MPNs are rare and typically develop slowly in older adults. Due to this, many patients have comordities, which can make treatment more difficult. The aim of treatment is to control the symptoms by reducing excessive numbers of blood cells in the circulation.
Many MPNs are related to specific acquired mutations, such as those in JAK2, MPL and CALR, which all lead to an overactive JAK2 protein. This has led to research focusing on targeted therapy in these areas, such as ruxolitnib, a JAK1/2 inhibitor which is approved for the treatment of PV and MF. Exciting developments include further JAK signaling inhibitors, Nutlins which act upon the p53 signaling pathway and novel drug combinations.
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