Myeloproliferative neoplasm

The myeloproliferative neoplasms (MPNs), previously myeloproliferative diseases (MPDs), are a group of diseases of the bone marrow in which excess cells are produced. They are related to, and may evolve into, myelodysplastic syndrome and acute myeloid leukemia, although the myeloproliferative diseases on the whole have a much better prognosis than these conditions. The concept of myeloproliferative disease was first proposed in 1951 by the hematologist William Dameshek. In the most recent World Health Organization classification of hematologic malignancies, this group of diseases was renamed from 'myeloproliferative diseases' to 'myeloproliferative neoplasms'. This reflects the underlying clonal genetic changes that are a salient feature of this group of disease. The myeloproliferative neoplasms (MPNs), previously myeloproliferative diseases (MPDs), are a group of diseases of the bone marrow in which excess cells are produced. They are related to, and may evolve into, myelodysplastic syndrome and acute myeloid leukemia, although the myeloproliferative diseases on the whole have a much better prognosis than these conditions. The concept of myeloproliferative disease was first proposed in 1951 by the hematologist William Dameshek. In the most recent World Health Organization classification of hematologic malignancies, this group of diseases was renamed from 'myeloproliferative diseases' to 'myeloproliferative neoplasms'. This reflects the underlying clonal genetic changes that are a salient feature of this group of disease. The increased numbers of blood cells may not cause any symptoms, but a number of medical problems or symptoms may occur. The risk of thrombosis is increased in some types of MPN. Although a malignant neoplasm like other cancers, MPNs are classified within the hematological neoplasms. There are four main myeloproliferative diseases, which can be further categorized by the presence of the Philadelphia chromosome: In 2008, the World Health Organization listed these diagnoses as types of MPD: All MPNs arise from precursors of the myeloid lineages in the bone marrow. The lymphoid lineage may produce similar diseases, the lymphoproliferative disorders (acute lymphoblastic leukemia, lymphomas, chronic lymphocytic leukemia and multiple myeloma). Most Philadelphia chromosome negative cases have an activating JAK2 or MPL mutation. Mutations in CALR have been found in the majority of JAK2 and MPL-negative essential thrombocythemia and myelofibrosis. In 2005, the discovery of the JAK2V617F mutation provided the first evidence that a fraction of persons with these disorders have a common molecular pathogenesis. Patients with JAK2V617F-negative polycythemia vera are instead positive for another class of activating JAK2 mutations - the JAK2 exon 12 mutations. A subset may additionally have mutations in the genes LNK, CBL, TET2, ASXL1, IDH, IKZF1 or EZH2; the pathogenetic contribution of these mutations is being studied. Depending on the nature of the myeloproliferative neoplasm, diagnostic tests may include red cell mass determination (for polycythemia), bone marrow aspirate and trephine biopsy, arterial oxygen saturation and carboxyhaemoglobin level, neutrophil alkaline phosphatase level, vitamin B12 (or B12 binding capacity), serum urate or direct sequencing of the patient's DNA. According to the WHO Classification of Hematopoietic and Lymphoid Neoplasms 2008 myeloproliferative neoplasms are divided into categories by diagnostic characteristics as follows: