Multiple myeloma is cancer of the plasma cells in the bone marrow. Although it may affect the bone, the disease is considered a type of blood cancer.

Cancers of the plasma cells are known as plasma cell neoplasms. Plasma cells are part of the immune system, a network of specialized cells and organs throughout the body designed to recognize foreign substances, such as  toxins, viruses, bacteria and parasites.

The main type of immune system cell is the lymphocyte. The two types of lymphocytes are B lymphocytes (B-cells) and T lymphocytes (T-cells). When B-cells react to an infection, they mature and become plasma cells. When these cells grow uncontrollably, they can produce a tumor. Usually, these tumors develop in the bone marrow. Bone marrow is the soft, inner component of bone. It produces all forms of blood cells, including:

• White blood cells. Cells that fight infection.
• Red blood cells. Cells that carry oxygen to tissues all over the body.
  
• Platelets. Cells that help develop blood clots and control bleeding.

When only one tumor develops, it is known as a solitary plasmacytoma. More often, there are numerous tumors spread throughout the body or diffuse penetration of the bone marrow by plasma cells. This disorder is known as multiple myeloma. The overgrowth of plasma cells can make it difficult for bone marrow to produce adequate numbers of normal blood cells. Eventually this can result in a shortage of white blood cells (leukopenia), red blood cells (anemia), and platelets (thrombocytopenia). Shortages in these types of cells can lead to a decreased ability to fight off infection, fatigue and excessive bleeding.

The exact cause of multiple myeloma has not been identified. Researchers, however, have gained a greater understanding of how specific changes in DNA can cause plasma cells to become cancerous. A number of risk factors have been identified, including age and having other plasma cell diseases. 

Symptoms of multiple myeloma vary based on the extent of the disease. Common signs and symptoms include bone pain, fatigue, weakness and recurrent infection.

Multiple myeloma may be first detected in routine blood tests. However, additional tests, including bone marrow tests, may be necessary to verify the diagnosis. The treatment and prognosis for multiple myeloma depends on the stage of the disease as well as other factors including the patient’s age and general health. Treatment may include bone marrow/stem cell transplantation, chemotherapy and radiation therapy. In many case, patients may receive a combination of these therapies.

According to the American Cancer Society (ACS), almost 20,000 new cases of multiple myeloma will be diagnosed in the United States in 2007. Of these new cases, approximately 10,900 will occur in men and 8,900 in women. The disease is also about twice as common among African Americans as it is among white Americans.