Multiple myeloma is a neoplastic proliferation of plasma cells which is characterized by bone destruction and the presence of increased monoclonal immunoglobulin and light chain proteins in the blood and urine.  It is the most common primary bone tumor.  Patients most commonly present with lower back pain and anemia.  98% of cases occur in those over 40 years of age.  The median age is 62 with a male predominance (3:2).  Patients also develop pathological fractures secondary to lytic destruction of bones, renal failure, increased susceptibility to infection, hypercalcemia, neurological symptoms, and clotting abnormalities.  The cause is unknown: however, atomic bomb survivors and radiologists have increased risk. 

Cytokines secreted by the myeloma (TNF-B, IL-1, IL-6, and M-CSF) play a major role in plasma cell differentiation and are largely responsible for the bony destruction due to their osteoclast-activating effects.  In 99% of cases, blood protein electrophoresis reveals highly increased levels of immunoglobulins.  55% have an elevation of the M-component of IgG (M spike).  Moreover, free kappa and lambda light chain (Bence-Jones proteins) can be detected in the urine.  Bone marrow analysis will reveal increased plasma cells. 

Radiographically, one sees the punched out lesions on skeletal survey.  These multifocal lesions with a "moth-eaten" appearance occur in 70% of patients.  The most commonly affected sites are the vertebral column (66%), ribs (44%), skull (41%), pelvis (28%), femur (24%), clavicle (10%), and scapula (10%).  A small percentage of cases can appear as either solitary cystic bone lesions or as generalized osteopenia.

Prognosis for multiple myeloma depends on the degree of tumor burden.  Patients with high burden (extensive bony destruction, high degree of anemia, hypercalcemia, and decreased renal function) have a median survival time of 2 years.  Low tumor burden patients have a median survival time of 5 years from time of diagnosis.  There is no cure for multiple myeloma.   Current therapy consists of intermittent courses of chemotherapy together with supportive care.  Bone marrow transplantation has had mixed results and is being researched extensively.  Death frequently occurs from bacterial infection and renal insufficiency. 

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