Myelofibrosis is a rare and chronic bone marrow disorder. It is characterized by the abnormal development and growth of blood cells in the bone marrow, leading to the formation of scar tissue (also called fibrosis) within the marrow. This disrupts the normal production and function of blood cells.
In myelofibrosis, there is a mutation in the stem cells, which are responsible for producing red blood cells, white blood cells and platelets. This mutation causes an overproduction of abnormal blood cells, particularly megakaryocytes (a type of bone marrow cell that produces platelets). These abnormal cells release growth factors that trigger the deposition of fibrous tissue in the bone marrow.
As the fibrosis progresses, it replaces the healthy bone marrow, which impairs its ability to produce an adequate number of blood cells. Consequently, the bone marrow attempts to compensate by moving the production of blood cells to other organs, such as the spleen and liver, leading to their enlargement.
In advanced stages, it can also lead to complications such as portal hypertension (high blood pressure in the portal vein that carries blood from the intestines to the liver) and an increased risk of developing acute leukemia.
Types of Myelofibrosis
There are different types of myelofibrosis, primarily categorized based on their origin and progression. The two main types are:
Primary myelofibrosis (PMF): Primary myelofibrosis is often referred to as idiopathic myelofibrosis, meaning its cause is unknown. It is considered a primary disease of the bone marrow.
Secondary myelofibrosis: Some cases of myelofibrosis may develop as a secondary condition in individuals who previously had polycythemia vera or essential thrombocythemia.
Why Do People Get Myelofibrosis?
The exact cause of myelofibrosis is not known. However, certain factors are believed to increase the risk of developing this disease. These include:
- Age: Myelofibrosis is more commonly diagnosed in older adults, with the majority of cases occurring in individuals over the age of 50
- Gender: Males are slightly more likely than females to get myelofibrosis
- Genetic mutations: Certain genetic mutations have been associated with an increased risk of developing myelofibrosis. Mutations in genes such as JAK2, CALR, and MPL are commonly found in individuals with myelofibrosis
- Previous blood disorders: Individuals who have had other myeloproliferative neoplasms (MPNs) such as polycythemia vera (PV) or essential thrombocythemia (ET) may be at an increased risk of developing myelofibrosis
- Exposure to radiation or chemicals: Prolonged exposure to high levels of radiation or certain chemicals may increase the risk of developing myelofibrosis
- Family history: A family history of myeloproliferative disorders or blood cancers may contribute to an individual's susceptibility to myelofibrosis
- Immune system disorders: Some autoimmune diseases or disorders that affect the immune system may be associated with an increased risk of myelofibrosis
It's important to note that having one or more risk factors does not mean that a person will definitely develop myelofibrosis. Many people with these risk factors never develop the disease, and many people who do develop myelofibrosis have no known risk factors.