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Causes
By Mayo Clinic staff
Although the exact cause isn't known, doctors do know that multiple myeloma begins with one abnormal plasma cell in your bone marrow — the soft, blood-producing tissue that fills in the center of most of your bones. This abnormal cell then starts to multiply.
Because abnormal cells don't mature and then die as normal cells do, they accumulate, eventually overwhelming the production of healthy cells. In healthy bone marrow, less than 5 percent of the cells are plasma cells. But in people with multiple myeloma, more than 10 percent of the cells may be plasma cells.
Because myeloma cells may circulate in low numbers in your blood, they can populate bone marrow in other parts of your body, even far from where they began. That's why the disease is called multiple myeloma. Uncontrolled plasma cell growth can damage bones and surrounding tissue. It can also interfere with your immune system's ability to fight infections by inhibiting your body's production of normal antibodies.
Researchers investigating cause
Researchers are studying the DNA of plasma cells to try to understand what changes occur that cause these cells to become cancer cells. Though they haven't yet discovered the cause of these changes, they have found that almost all people with multiple myeloma have genetic abnormalities in their plasma cells that probably contributed to the cancer. For example, many myeloma cells are missing all or part of one chromosome — chromosome 13. Cells with a missing or defective chromosome 13 tend to be more aggressive and harder to treat than are cells with a normal chromosome 13.
A connection with MGUS
Multiple myeloma almost always starts out as a relatively benign condition called monoclonal gammopathy of undetermined significance (MGUS). In the United States, about 3 percent of people over the age of 50 have MGUS. Each year, about 1 percent of people with MGUS develop multiple myeloma or a related cancer. This condition, like multiple myeloma, is marked by the presence of M proteins — produced by abnormal plasma cells — in your blood. However, in MGUS, no damage to the body occurs.
- Rajkumar SV, et al. Multiple myeloma and related disorders. In: Abeloff MD, et al. Abeloff's Clinical Oncology. 4th ed. Philadelphia, Pa.: Churchill Livingstone; 2008. http://www.mdconsult.com/das/book/body/145977116-5/856340478/1709/160.html#4-u1.0-B978-0-443-06694-8..50114-7_4940. Accessed June 12, 2009.
- Konrad CN, et al. Multiple myeloma: Diagnosis and treatment. American Family Physician. 2008;78:853.
- Rajkumar SV. Initial chemotherapy for patients with high risk multiple myeloma. http://www.uptodate.com/home/index.html. Accessed June 12, 2009.
- Rajkumar SV. Initial chemotherapy for symptomatic multiple myeloma in patients who are not candidates for transplantation. http://www.uptodate.com/home/index.html. Accessed June 12, 2009.
- Treatment of the complications of multiple myeloma. http://www.uptodate.com/home/index.html. Accessed June 12, 2009.
- Detailed guide: Multiple myeloma. Chemotherapy and other drugs. American Cancer Society. Accessed June 12, 2009.
- Multiple myeloma: Moving on after treatment. American Cancer Society. Accessed June 12, 2009.
- Richardson PG, et al. Management strategies for relapsed multiple myeloma: Therapy in practice. American Journal of Cancer. 2006;5:393.
- Detailed guide: Multiple myeloma. What are the risk factors for multiple myeloma? American Cancer Society. Accessed June 12, 2009.
- Multiple myeloma: What are some questions I can ask my doctor? American Cancer Society. Accessed June 12, 2009.
- Integrative medicine & complementary and alternative therapies as part of blood cancer care. The Leukemia & Lymphoma Society. http://www.leukemia-lymphoma.org/attachments/National/br_1150734030.pdf. Accessed June 12, 2009.
- Complementary and alternative methods for cancer management. American Cancer Society. http://www.cancer.org/docroot/ETO/content/ETO_5_1_Introduction.asp. Accessed June 12, 2009.
- Rajkumar SV (expert opinion). Mayo Clinic, Rochester, Minn. July 8, 2008.
