Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Multiple myeloma is cancer of the bone marrow caused by the uncontrolled growth of plasma cells. These cells are one type of white blood cells. Normally, they make antibodies called immunoglobulins to fight infections.

In multiple myeloma, cancerous plasma cells multiply rapidly in the bone marrow and invade the outer layers of the bones. They also make too much of one specific type of immunoglobulin (an antibody protein). Large amounts of immunoglobulins in the bloodstream may cause the blood to become thick and sticky. This can lead to blood clots.

In multiple myeloma, the blood levels of other antibodies drop, leaving the person open to infections.

Other problems that occur in people with multiple myeloma include

  • high blood calcium levels, which can lead to dehydration, constipation, and confusion

  • impaired kidney function

  • low red blood cell counts (anemia).

A variant of multiple myeloma is called plasmacytoma. A plasmacytoma is a single collection of abnormal plasma cells in only one bone. Plasmacytomas cause bone pain but usually don't cause the problems associated with multiple myeloma.

Multiple myeloma is an uncommon cancer. It tends to occur in older people, developing around age 60. Other risk factors include exposure to

  • radiation

  • a toxic chemical called benzene

  • pesticides.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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