Monoclonal gammopathy of undetermined significance (MGUS)
In this type of plasma cell neoplasm, less than 10% of the bone marrow is 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.
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.
- Feeling very tired.
- Muscle weakness.
- Confusion or trouble thinking.