Multiple myeloma is a relatively rare cancer of the bone. It occurs when the body produces too many abnormal plasma cells, which are called myeloma cells. Plasma cells normally produce antibodies. Antibodies are part of the immune system. They attack germs and help protect the body from infections.

Cancer occurs when cells in the body (in this case plasma cells) divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and can spread to other parts of the body.

Myeloma cells collect and grow in the bone marrow, the soft interior of the bone. This often results in decreased production of blood cells:

  • Red blood cells, which carry oxygen to the body
  • White blood cells, which help fight off infection
  • Platelets, which help the blood to clot

When myeloma cells grow in more than one site, the disease is called multiple myeloma. A single tumor of abnormal plasma cells is called a solitary plasmacytoma.


The cause of multiple myeloma is not known. Doctors think exposure to toxins, radiation, or a virus may play a role. Inherited gene mutations may also lead to multiple myeloma. In nearly all cases, doctors have no idea why a particular person develops the disease.

About 14,600 Americans are diagnosed with multiple myeloma each year. Slightly more men than women are affected. And 10,800 people with the disease die from it annually. Multiple myeloma affects older adults. The average age of people with this disease is 65. It is very uncommon for myeloma to occur in people younger than 40.


Because multiple myeloma affects blood production, complications of the disease typically relate to problems with blood function. These complications include the following:

  • ]]>Anemia]]>—This is characterized by a lack of red blood cells, which carry oxygen to the body’s cells. Anemia causes fatigue because the cells do not receive enough oxygen. It can also aggravate a heart condition in a person with ]]>angina]]> or other heart disease, in which the heart is already suffering from insufficient blood supply. The additional lack of oxygen in the blood from anemia compounds the problem.
  • Increased risk of infection—Because there are not enough white cells to fight bacteria, viruses, and other microbes, infection is more likely.
  • Easy bleeding—Decreased production of platelets impairs blood clotting ability, leading to easy and prolonged bleeding.

As malignant plasma cells multiply, they produce enormous quantities of abnormal antibodies. These abnormal antibodies accumulate in the blood and urine. This can cause kidney damage and a weakened immune system. About 20% of patients with the disease develop kidney problems and most find themselves more susceptible to infections. The antibodies can also cause the blood to thicken. This can, in turn, decrease circulation to the brain, which can result in ]]>stroke]]>. Decreased circulation to other organs can cause death of tissues in those organs as well.

The growing tumor may destroy the surrounding bone, which leads to bone pain. Bones may break as they weaken. The bones in the spine may collapse and put pressure on the spinal cord, creating a medical emergency. Destruction of the bone also leads to high levels of calcium in the blood. Too much calcium can cause weakness and confusion, which can mimic stroke or dementia, such as in ]]>Alzheimer's disease]]>.

Myeloma is also associated with ]]>amyloidosis]]>. This is a rare condition in which abnormal proteins accumulate in various organs of the body. The accumulation of these proteins causes the involved organs (usually heart, muscle, nervous system, and intestines) to malfunction. Amyloidosis is the result of a malfunction in the plasma cells that make antibodies. It is sometimes associated with myeloma. Anyone diagnosed with amyloidosis probably needs to be evaluated for the presence of myeloma. Patients with myeloma will sometimes experience complications as a result of amyloidosis.