What Causes Myelofibrosis?

Patients develop myelofibrosis -- also referred to as chronic ideopathic myelofibrosis and myeloid metaplasia -- when red blood stem cells in bone marrow mutate, eventually causing the marrow to scar. Researchers have yet to determine the exact cause of the mutation, although several risk factors for the disorder's development have been identified. Studies have found that a significant number of patients with myelofibrosis had a preexisting blood cell disorder. Experts believe that exposure to certain chemicals and types of radiation can also increase the risk of developing myelofibrosis. Age might also be a factor, as the majority of cases occur in individuals aged 50 years and older.

The genetic mutation involved in myelofibrosis occurs in stem cells found in bone marrow; under normal circumstances, these cells develop into red blood cells. An unknown trigger causes the cells to malfunction, severely limiting red blood cell production, which, in turn, results in anemia. The stem cells then divide; any new cells formed from the division carry the mutation as well, eventually spreading throughout the bone marrow. A deficiency in red blood cells and a surplus of white blood cells can cause scar tissue to develop in the bone marrow, a characteristic symptom of myelofibrosis.

Although the cause of the mutation is generally unknown, researchers believe that certain blood disorders increase the risk a patient has of developing myelofibrosis. Polycythemia vera, a disease in which red blood cells proliferate at abnormally high rates, tends to increase the likelihood that a mutation in the cells will occur and spread. Essential thrombocytosis, in which the bone marrow produces an overabundance of platelets, heightens the risk in a similar fashion.

Another risk factor associated with myelofibrosis is the overexposure to certain industrial chemicals. Toluene, a commonly-used chemical solvent, has been identified as a substance that might lead to the development of the condition. The chemical is used in many industrial procedures, including cementing polystyrene, dissolving paint, and even in producing cola syrup. The amounts individuals are exposed to in everyday life are generally considered safe, however, with unsafe exposure being a rarity.

A significant number of patients diagnosed with myelofibrosis falls in the 50 to 70 age range, leading some experts to believe that age plays a factor in its development. Older bone marrow might be more prone to mutation, although it is not clear how. Individuals aged 50 and older might also have been exposed to risk factor chemicals more than younger people, indicating a possibility that the effects of harmful chemical exposure can be cumulative.