Our bone marrow is formed by cells that divide and differentiate to transform into mature cells found in our bloodstream. They include red cells, white cells and platelets. The rate of division and differentiation is controlled by many feedback mechanisms which make sure that the rate of division equals the need for new cells, either due to the destruction of old ones or the increased overall needs of the body.
For example, the increased white blood cell count during infections. Disruption of such mechanisms causes what is collectively known as myeloproliferative neoplasms, which is the uncontrolled division of one or more of those cell lines. The reason is at the genetic level in the form of a mutation or a critical change of the genetic constitution of those cells. If you have previous knowledge about leukemia, the mechanism seems familiar, and that is because it is. Acute leukemias are a known consequence of myeloproliferative neoplasms.
Myeloproliferative neoplasms include the following diseases, according to the latest classification:
- Chronic myelogenous leukemia (CML): This is the only myeloproliferative neoplasm with characteristic Philadelphia chromosome mutation.
- Essential thrombocythemia (ET)
- Polycythemia rubra vera (PV)
There are other minor disorders that may be considered as MPN, including mastocytosis and chronic neutrophilic leukemia, but this is still subject to clinical debate, so we will only focus on the 4 main types.
1) Primary myelofibrosis
When myelofibrosis is mentioned, it generally refers to primary myelofibrosis. The reason it is called primary or “idiopathic” is that there is no known cause for its occurrence and it is not preceded by another condition that eventually caused it.
2) Secondary myelofibrosis
This refers to myelofibrosis that developed following polycythemia vera or essential thrombocythemia as a complication.
Continue reading to uncover the mechanism of its occurrence now.