Multiple myeloma is often referred to simply as myeloma. It is a type of cancer that starts in the plasma cells of the bone marrow. These are protein-making cells which normally make all of the different kinds of proteins that comprise the antibodies of the immune system. In multiple myeloma, the plasma cells undergo what is referred to as a malignant transformation and thereby become cancerous. These myeloma cells stop making different forms of protein in response to the immune system's needs and instead start to produce a single abnormal type of protein referred to as a monoclonal or M protein. Multiple myeloma plasma cell populations accumulate and these collections of cells called plasmacytomas can erode the hard outer shell or cortex of the bone that normally surrounds the marrow. These weakened bones show thinning of the bone such as is seen in nonmalignant osteoporosis or what appear to be punched out or lytic bone lesions. These lesions may cause pain and even breaks or fractures of the bones so damaged. They may cause other systemic problems listed below.

Signs and symptoms of multiple myeloma can vary and, early in the disease, there may be none.

When signs and symptoms do occur, they can include:

• Bone pain, especially in your spine or chest
• Nausea
• Constipation
• Loss of appetite
• Mental fogginess or confusion
• Fatigue
• Frequent infections
• Weight loss
• Weakness or numbness in your legs
• Excessive thirst

When to see a doctor

Make an appointment with your doctor if you have any persistent signs and symptoms that worry you.

It's not clear what causes myeloma.

Doctors know that myeloma begins with one abnormal plasma cell in your bone marrow — the soft, blood-producing tissue that fills in the center of most of your bones. The abnormal cell multiplies rapidly.

Because cancer cells don't mature and then die as normal cells do, they accumulate, eventually overwhelming the production of healthy cells. In the bone marrow, myeloma cells crowd out healthy white blood cells and red blood cells, leading to fatigue and an inability to fight infections.

The myeloma cells continue trying to produce antibodies, as healthy plasma cells do, but the myeloma cells produce abnormal antibodies that the body can't use. Instead, the abnormal antibodies (monoclonal proteins, or M proteins) build up in the body and cause problems such as damage to the kidneys. Cancer cells can also cause damage to the bones that increases the risk of broken bones.

A connection with MGUS

Multiple myeloma almost always starts out as a relatively benign condition called monoclonal gammopathy of undetermined significance (MGUS).

In the United States, about 3 percent of people older than age 50 have MGUS. Each year, about 1 percent of people with MGUS develop multiple myeloma or a related cancer.

MGUS, like multiple myeloma, is marked by the presence of M proteins — produced by abnormal plasma cells — in your blood. However, in MGUS, the levels of M proteins are lower and no damage to the body occurs.

There is no known treatment that cures multiple myeloma. However, there are methods to decrease the occurrence and severity of symptoms and prolong life. The therapy is decided based upon the patient's condition and the cancer management team, made with the patient's input. The team will likely involve both a medical specialist in the treatment of myeloma called a medical oncologist, as well as a radiation oncologist and other consultants as appropriate. Oncology trained nurses and other personnel will likely be important members of the treatment team.

The choices for treatment(s) often include combinations drugs, some of which are given as pills and others by intravenous injection. These include drugs which affect or modulate the immune system, steroids, and some oral or injectable chemotherapy drugs. These are usually used in combinations. There may be a role for high-dose chemotherapy followed by the administration of bone marrow stem cells called a stem cell transplant. Numerous factors come into play in determining whether or not to do such a transplant. Further information may be obtained from the National Comprehensive Cancer Network Guidelines (NCCN.org) which are updated at least yearly.

Painful areas of bone damage may be treated with radiation therapy. Broken bones can be surgically repaired in many cases.

There are many drugs used to treat multiple myeloma. Research is ongoing and newer drugs are being investigated and used for treatment with some frequency. For example, a clinical trial in 2013 reported that lenalidomide (Revlimid) produced a significant increase in the survival of individuals newly diagnosed multiple myeloma. Most doctors who specialize in cancer treatment will be aware of the newest treatments for multiple myeloma.

Factors that may increase your risk of multiple myeloma include:

• Increasing age. Your risk of multiple myeloma increases as you age, with most people diagnosed in their mid-60s.
• Male sex. Men are more likely to develop the disease than are women.
• Black race. Black people are about twice as likely to develop multiple myeloma as are white people.
• Family history of multiple myeloma. If a brother, sister or parent has multiple myeloma, you have an increased risk of the disease.
• Personal history of a monoclonal gammopathy of undetermined significance (MGUS). Every year 1 percent of the people with MGUS in the United States develop multiple myeloma.