Normal white blood cells are produced in the bone marrow, the soft spongy tissue that fills most of our bones. Some white blood cells develop into plasma cells, which help the immune system to fight infection by developing antibodies. They develop specific antibodies to fight specific diseases or infections.
Sometimes, the body’s production of plasma cells gets out of control, well beyond the body’s need to fight infection and disease. These unneeded cells are called myeloma cells and they group together in the marrow or in the hard part of the bone. When they collect only in one bone and form a single mass, the resulting tumor is known as a plasmacytoma.
In most cases, though, the cancer affects many bones, forming tumors and causing other problems. When this happens, the disease is known as multiple myeloma (MM). Approximately 13,000 Americans are diagnosed with multiple myeloma every year.
Plasma Cells: Antibody-Producing Lymphocytes. Plasma cells are essentially specialized white blood cells, also called B cells, or B-lymphocytes. Normally, plasma cells comprise only five percent of blood cells.
Myeloma occurs when abnormal B-lymphocytes begin to reproduce at a rapid rate, producing large quantities of antibodies. The excess of lymphocytes in the bone marrow hinders the production of other blood cells, in effect “crowding out” healthy blood cells. Eventually the cancer cells spread to hard bone tissue.
Blood or Bone Cancer? Multiple myeloma is often called bone cancer. In medical terms, this is not strictly accurate. Cancers are usually labeled according to their origin. For example, if cancer begins in the liver then spreads to other parts of the body such as the lungs or the kidneys, the patient is said to have cancer of the liver because that’s where it originated.
Although myeloma affects the skeletal system, the disease begins in the blood, and then spreads to the skeletal system. Thus, it’s more accurate to label multiple myeloma as a blood disease than to call it a bone cancer.
Causes of Myeloma
The exact cause of multiple myeloma remains unknown. Medical researchers have concluded that people in certain occupations appear to have a higher risk of developing MM than others.
These include farmers, petrochemical workers, leather workers and cosmetologists. Chemical and herbicide exposure in these occupations may account for the greater risk.
Radiation is also a known risk factor. Twenty years after the World War II nuclear attacks on Japan, multiple myeloma rates in the country were found to have increased significantly.
Researchers have also discovered a possible connection between multiple myeloma and a strain of the herpes virus known as Kaposi’s sarcoma-associated herpes virus. Clinical trials are investigating treatments based on this connection, hoping to shed more light on the origins of the cancer.
Multiple myeloma is an uncommon disease, affecting on average 3 out of every 100,000 people. The cancer is usually diagnosed after age forty, with 68 being the average age of diagnosis. Men are more susceptible to the disease: 1.6 men are diagnosed for every woman.
African Americans are twice as likely as Caucasians to develop the disease: multiple myeloma is one of the top ten causes of cancer deaths in African Americans. Native Pacific islanders are also at greater risk than Caucasians, while people of Asian ethnicity have the lowest incidence rates.
Bone Pain and Other Symptoms
Often, no symptoms appear in the early stages of the disease. In later stages, bone pain is the most common symptom. The bone pain is most often localized in the back and ribs. The pain can be severe enough to affect the patient’s mobility.
As the disease progresses, patients may develop osteoporosis, suffering fractures and abnormal bone lesions. Blood tests may indicate anemia (a lack of red blood cells) or hypercalcemia (excess calcium in the blood).