Causes and Risk Factors
Doctors don't know why some cells become myeloma cells and others don't. For most people who have myeloma, there are no obvious reasons why they developed the disease.
There are some factors that may increase the risk of developing myeloma, including
- Age - Most people who develop myeloma are over age 50 years. Few cases of myeloma occur in people younger than 40.
- Sex - More men develop myeloma than women.
- Race - African Americans are nearly twice as likely to develop myeloma as are whites (Caucasians).
- Medical History - People who have a prior history of the diagnosis MGUS (monoclonal gammopathy of unknown significance).
- Environment - Some studies are showing a link between the development of myeloma and smoking, radiation, or exposure to certain kinds of chemicals such as pesticides, fertilizers and Agent Orange (see A Risk for Vietnam Veterans below).
- Obesity - New research suggests that people who are obese have a higher incidence of myeloma.
A Risk for Vietnam Veterans
The National Academy of Sciences suspects there may be a link between myeloma and exposure to herbicides like Agent Orange used during the Vietnam conflict from 1961 to 1971. If you have myeloma and think you may have been exposed to Agent Orange or other herbicides, you may be entitled to disability compensation from the U.S. Department of Veterans Affairs. For more information, visit the U.S. Department of Veterans Affairs website.
How Does Myeloma Develop?
Myeloma starts with one or more changes to the DNA of a single stem cell in the bone marrow. Stem cells form blood cells (white cells, red cells and platelets).
Myeloma develops in a white cell called a B lymphocyte (B cell). Some lymphocytes transform plasma cells, which make antibodies. In myeloma, an injury to a B cell's DNA causes an abnormal change that can start the transformation of a normal plasma cell into a cancerous cell.
The cancerous cells multiply at a faster rate than normal cells and don't die off when they should. They eventually crowd out functioning cells. Most of the cancerous cells are confined to the marrow, but sometimes they circulate in the blood. If not treated, the cancerous cells can:
- crowd out functioning white cells, and the immune system can't guard against infection effectively
- secrete high levels of protein in the blood and urine, which can lead to kidney damage
- build up in bone, causing it to weaken, which can lead to bone pain and fractures