Multiple myeloma (from Greek myelo-, bone marrow), also known as plasma cell myeloma or Kahler's disease (after Otto Kahler), is a cancer of plasma cells, a type of white blood cell normally responsible for the production of antibodies. Collections of abnormal cells accumulate in bones, where they cause bone lesions (abnormal areas of tissue), and in the bone marrow where they interfere with the production of normal blood cells. Most cases of myeloma also feature the production of a paraprotein, an abnormal antibody that can cause kidney problems and interferes with the production of normal antibodies leading to immunodeficiency. Hypercalcemia (high calcium levels) is often encountered.
Myeloma is diagnosed with blood tests (protein electrophoresis, peripheral blood smear), microscopic examination of the bone marrow (bone marrow biopsy), and radiographs of commonly involved bones. Myeloma is generally thought to be incurable, but remissions may be induced with steroids, chemotherapy, thalidomide and stem cell transplants. Newer drugs, such as lenalidomide and bortezomib, are often used in more advanced disease. Radiation therapy is sometimes used to treat bone lesions that are causing symptoms.
The disease develops in 1–4 per 100,000 people per year. It is more common in men, and for yet unknown reasons is twice as common in African Americans as it is in white Americans. With conventional treatment, the prognosis is 3–4 years, which may be extended to 5–7 years or longer with advanced treatments. Multiple myeloma is the least common hematological malignancy (14%) and constitutes 1% of all cancers.