Multiple Myeloma is a type of blood cancer that affects plasma cells, a type of white blood cells (WBC). These WBC's are part of your immune system, which helps protect the body from germs and other harmful pathogens. In multiple myeloma, the malignant overgrowth of plasma cells in the bone marrow can simply crowding out the normal plasma cells. These malignant plasma cells then produce an abnormal antibody known as M protein, which offers no benefit to the body and may cause tumors, kidney damage, bone destruction, and impaired immune function. The hallmark characteristic of multiple myeloma is a high level of M protein in the blood.

There are, however, other plasma cell disorders that also have abnormal plasma cells but do not meet the criteria to be called active multiple myeloma. These other plasma cell disorders include:

• Monoclonal gammopathy of uncertain significance (MGUS)
• Smouldering multiple myeloma (SMM)
• Solitary plasmacytoma
• Light chain amyloidosis.

No one knows the exact causes of multiple myeloma, but it is more common in older people and African Americans. It can run in families. Common symptoms may include:

• Bone pain, often in the back or ribs
• Broken bones
• Weakness or fatigue
• Weight loss
• Frequent infections and fevers
• Feeling very thirsty
• Frequent urination

Doctors diagnose multiple myeloma using:

• Lab tests
• Imaging tests
• Bone marrow biopsy

Your treatment depends on how advanced the disease is and whether you have symptoms. 
If you have symptoms, you may have chemotherapy, stem cell transplantation, radiation, or targeted therapy. Targeted therapy uses substances that attack cancer cells without harming normal cells.