What is multiple myeloma?

Multiple myeloma (MM) is a type of blood cancer formed from plasma cells which are a type of white blood cell that lives in the bone marrow. MM is one of several types of plasma cell neoplasms that are diseases in which the body makes too many plasma cells.

Plasma cells develop from B lymphocytes (B cells), a type of white blood cell that is made in the bone marrow. Normally, when bacteria or viruses enter the body, some of the B cells will change into plasma cells. The plasma cells make antibodies to fight bacteria and viruses, to stop infection and disease.

Plasma cell neoplasms are diseases in which abnormal plasma cells or myeloma cells form tumors in the bones or soft tissues of the body. The plasma cells also make an antibody protein, called M protein, that is not needed by the body and does not help fight infection. These antibody proteins build up in the bone marrow and can cause the blood to thicken or can damage the kidneys.

Multiple Myeloma is a type of plasma cell neoplasm that is cancer.

In multiple myeloma, abnormal plasma cells (myeloma cells) build up in the bone marrow and form tumors in many bones of the body. These tumors may keep the bone marrow from making enough healthy blood cells. Normally, the bone marrow makes stem cells (immature cells) that become three types of mature blood cells:

Red blood cells that carry oxygen and other substances to all tissues of the body.
White blood cells that fight infection and disease.
Platelets that form blood clots to help prevent bleeding.

As the number of myeloma cells increases, fewer red blood cells, white blood cells, and platelets are made. The myeloma cells also damage and weaken the bone.

Sometimes multiple myeloma does not cause any signs or symptoms. This is called smoldering multiple myeloma. It may be found when a blood or urine test is done for another condition. Signs and symptoms may be caused by multiple myeloma or other conditions. Check with your doctor if you have any of the following:

Bone pain, especially in the back or ribs.
Bones that break easily.
Fever for no known reason or frequent infections.
Easy bruising or bleeding.
Trouble breathing.
Weakness of the arms or legs.
Feeling very tired.

A tumor can damage the bone and cause hypercalcemia (too much calcium in the blood). This can affect many organs in the body, including the kidneys, nerves, heart, muscles, and digestive tract, and cause serious health problems.

Hypercalcemia may cause the following signs and symptoms:

Loss of appetite.
Nausea or vomiting.
Feeling thirsty.
Frequent urination.
Constipation.
Feeling very tired.
Muscle weakness.
Restlessness.
Confusion or trouble thinking.

Multiple myeloma and other plasma cell neoplasms may cause a condition called amyloidosis.

In rare cases, multiple myeloma can cause peripheral nerves (nerves that are not in the brain or spinal cord) and organs to fail. This may be caused by a condition called amyloidosis. Antibody proteins build up and stick together in peripheral nerves and organs, such as the kidney and heart. This can cause the nerves and organs to become stiff and unable to work the way they should.

Amyloidosis may cause the following signs and symptoms:

Feeling very tired.
Purple spots on the skin.
Enlarged tongue.
Diarrhea.
Swelling caused by fluid in your body's tissues.
Tingling or numbness in your legs and feet.

Age can affect the risk of plasma cell neoplasms.

Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk with your doctor if you think you may be at risk.

Plasma cell neoplasms are most common in people who are middle aged or older. For multiple myeloma and plasmacytoma, other risk factors include the following:

Being black.
Being male.
Having a personal history of MGUS or plasmacytoma.
Being exposed to radiation or certain chemicals.

Lymphoplasmacytic lymphoma
Plasmacytoma
Multiple myeloma

Monoclonal gammopathy of undetermined significance (MGUS) is a form of non-cancerous plasma cell neoplasm which sometimes becomes multiple myeloma.

People with MGUS have less than 10% of their bone marrow made up of abnormal plasma cells and there is no cancer. The abnormal plasma cells make M protein, which is sometimes found during a routine blood or urine test. In most patients, the amount of M protein stays the same and there are no signs, symptoms, or health problems.

In some patients, MGUS may later become a more serious condition, such as amyloidosis, or cause problems with the kidneys, heart, or nerves. MGUS can also become cancer, such as multiple myeloma, lymphoplasmacytic lymphoma, or chronic lymphocytic leukemia.