Myelo is Greek for marrow. It all starts in the myelo, the blood producing factory encased in our bones. Within the marrow, the blood producing (haematopoietic) stem cell can clone itself for future operations, and can also develop into mature blood cells that will circulate throughout the body in one of three forms: red blood cells, white blood cells, and platelets. Since these stem cells can develop in different directions based, for example, on biochemical signals or mutations, it is possible for one line of stem cells to gain a competitive advantage, mature, clone itself, and upset haemostasis or the normal balance of cell types within the blood.

This disorder of the myelo due to the proliferation and domination of one or another cell elements is a myeloproliferative disorder. Since the process produces an excessive cell mass of one type or another it is also known as a myeloproliferative neoplasm.

Myeloproliferative neoplasms take their names based on the blood cell line that is multiplying aggressively. PV, or polycythemia vera is a condition where red blood cells proliferate. In ET, essential thrombocythemia, the runaway cell line are the platelets. In CML, chronic myeloid leukemia, the leukocytes or white blood cells dominate. The three main MPN disorders are PV, ET, and MF, or myelofibrosis, a scarring and fibrotic condition brought about through the impact on the marrow structure of the abnormal blood production activity.

Polycythemia Vera (PV)

Polycythemia vera is the MPN characterized by an excess of red blood cells. PV can include other blood cell anomalies, but the chief characteristic is an overproduction of RBCs producing the polycythemia (increased blood volume or haematocrit). While PV can be slow to develop, the effects of untreated polycythemia are serious. Along with headache, fatigue, dizziness and itching, are potentially life threatening effects such as stroke, deep vein thrombosis and heart attack. Routine treatment includes phlebotomy to reduce blood volumes, often causing iron deficiency anaemia and drugs such as hydroxyurea (hydroxycarbamide) and interferon.

Essential Thrombocythemia (ET)

Essential thrombocythemia is characterized by an excess of platelets (thrombocytes). Usually an indolent condition, ET can often remain untreated, however in advanced stages ET poses a danger of thrombotic (clotting) or haemorrhagic (bleeding) events and is treated with platelet reducing drugs, such an Anagrelide, or cytoreductive agents like hydroxyurea along with a daily low-dose aspirin.

Myelofibrosis (MF)

Myelofibrosis (MF) can also be known as AMM (agnogenic myeloid metaplasia), IMF (idiopathic myelofibrosis), PMF (primary myelofibrosis) and MMM (myelofibrosis with myeloid metaplasia). Myelofibrosis is a condition in which the marrow's production of blood cells is reduced through scarring and fibrosis, and can be a primary MPD or secondary to one of the other MPDs. Although there are promising clinical trials at this time there is no cure for myelofibrosis beyond bone marrow transplant. MF is progressive, creating severe fatigue, weakness and splenomegaly, when the spleen enlarges as it takes on an expanded role in storing and producing blood.

Chronic myeloid leukemia (CML)

Chronic myeloid leukemia (CML) is a cancer of the the blood-producing cells of the bone marrow. The disorder primarily results in an increase in the number of white blood cells, but in addition, the number of blood platelets can increase, and the number of red blood cells may decrease. CML is a type of myeloproliferative disorder that is associated with an acquired genetic mutation called the Philadelphia Chromosome. Recent advances in research have resulted in drugs such as Imatinib and other targeted therapies, which have considerably improved survival.

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