What Is MGUS? - Monoclonal Gammopathy of Undetermined Significance

MGUS is caused by monoclonal plasma cells. Monoclonal means we think they all began from the same cell.

Plasma cells are part of your immune system. When they are normal, they help you fight infection. Here’s how: When germs enter your body, special immune cells “take a bite” from them, and — with the help of other immune cells — present the pieces to the plasma cells to help them identify the enemy. The plasma cells then multiply themselves into an army and produce antibodies to kill the germs. The antibodies are made to attack those germs specifically, and fit into them like a key into a lock. (Plasma cells respond to vaccines and immunizations the same way — by making the antibodies that protect you against diseases such as the flu, measles and polio.)

As soon as the infection is gone, the plasma cells stop multiplying. Some of them go back into the bone marrow and stay there in case the germs return and they are needed again.

When plasma cells become abnormal, they do not stop multiplying, and they produce antibodies that are not targeted to specific germs, so they are useless in fighting infection.

The antibodies produced by those abnormal cells are called monoclonal proteins (M-proteins), and they can be measured in the blood and urine. If only parts of the antibodies are produced, they are called light or heavy chains.

MGUS risk factors

Who’s most at risk for developing MGUS?

  • Older people
  • African Americans
  • Men
  • Those with a family history of MGUS or multiple myeloma
  • Vietnam veterans and others exposed to the herbicide Agent Orange
  • Firefighters and other 9/11 first responders have about twice the average risk of developing MGUS.
  • Farmers and others who work in agriculture

Symptoms of MGUS

MGUS does not usually cause symptoms. However, in rare cases it can cause neuropathy, a type of nerve damage that can cause tingling, numbness or pain, mostly starting in the fingers and arms or toes and legs.

Some patients with MGUS may also develop renal problems when monoclonal proteins accumulate in the kidney tissue.

MGUS prognosis

MGUS is not a disease, because most of the time it causes no symptoms, but there is a very low risk that it can progress into a symptom-causing disease. When you are evaluated at Roswell Park, your team will look at your risk factors to determine the chances that that will happen.

Tests for diagnosing MGUS

The following tests may be required to diagnose MGUS and determine that it is not a symptom-causing disease:

  • Bone marrow biopsy, to find out how many monoclonal plasma cells are in your bone marrow (This is performed only in patients with certain characteristics of MGUS.)
  • A urine sample (collected over a 24-hour period) and blood draw, to find out how much M-protein is in your urine and serum.
  • A blood draw, to find out how much calcium is in your blood and whether your kidneys are functioning normally.
  • Magnetic Resonance Imaging (MRI) or Positron Emission Tomography and Computed Tomography (PET-CT), to find out whether there are holes in your bones (This is performed only in patients with certain characteristics of MGUS.)

Treatment of MGUS

Because MGUS does not cause symptoms, and the risk of developing symptoms is low, researchers agree that it does not have to be treated — only monitored with follow-up visits every six to 12 months.

Roswell Park’s Palliative Care team can assist patients who experience neuropathy due to MGUS or if it occurs as a side effect of treatment.

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