Causes and Risk Factors for Multiple Myeloma
The underlying cause for multiple myeloma is unknown; however, research has shown that the disease begins as a change (mutation) in genetic material called DNA (deoxyribonucleic acid) within plasma cells. This genetic material contains instructions that determine and control cell growth, division, and function.
Genes that increase cell growth and division are called oncogenes and genes that reduce cell growth and division or result in cell death are called tumor suppressor genes. In some cases, abnormalities in genetic material "switch on" cancer-promoting oncogenes and "switch off" cancer-preventing tumor suppressor genes, increasing the risk for multiple myeloma and other types of cancer.
Multiple myeloma cells also may contain abnormalities in DNA components called chromosomes. Each normal, healthy cell contains 46 chromosomes in 23 pairs. Translocation is a genetic error in which parts of two chromosomes are exchanged. When this error occurs near an oncogene, it can trigger abnormal cell growth and division and cause cancer.
In another chromosomal abnormality found in some myeloma cells, parts of chromosome 13 are missing. This genetic error increases the risk for multiple myeloma that is highly aggressive and difficult to treat. Patients with multiple myeloma also may have other bone marrow cell abnormalities that increase plasma cell growth and division.
Several risk factors for multiple myeloma have been identified. Some of these factors cannot be changed or avoided (called non-modifiable risk factors) and others can be avoided in some cases (called modifiable factors risk factors). Recent studies indicate that a combination of risk factors probably contributes to the development of multiple myeloma.
Multiple myeloma risk factors include the following:
- African American race
- Age (e.g., over the age of 65)
- Exposure to radiation (e.g., from x-rays, handling radioactive materials, or living near or working in nuclear energy production facilities)
- Family history of multiple myeloma (e.g., having a close relative, such as a sibling or parent, with the disease)
- Male gender
- Monoclonal gammopathy of unknown significance (MGUS)
Certain medical conditions and environmental or occupational exposures (e.g., to chemicals or viruses) may increase the risk for multiple myeloma, but the role of these factors is not completely understood. Some studies have shown that people with chronic infections (e.g., hepatitis C, HIV/AIDS) or autoimmune disorders (e.g., rheumatoid arthritis) are at higher risk for developing multiple myeloma. Environmental factors, including job-related exposure to metal, rubber, wood, paint, solvents, leather, fertilizers, pesticides, or petroleum products also may increase the multiple myeloma risk.
Monoclonal gammopathy of unknown significance (MGUS) is a condition characterized by the presence of M proteins in the blood without other evidence of multiple myeloma. MGUS usually does not cause symptoms; however, people with the condition are at higher risk for developing multiple myeloma, leukemia, and other disorders (e.g., connective tissue disorders, chronic skin diseases, neurological disorders) over time. People who have MGUS undergo regular blood tests to monitor the condition.