Other names: 

Monoclonal protein, myeloma protein, M-protein, M-spike

Test name: 

Urine protein electrophoresis (UPEP)

What is M-protein and M-spike?

- M-protein is an abnormal protein produced by myeloma cells that accumulates in and damages bone and bone marrow.

- Antibodies or parts of antibodies found in unusually large amounts in the blood or urine of myeloma patients.

- A monoclonal spike (M-Spike), the sharp pattern that occurs on protein electrophoresis, is the telltale indicator of M-protein in the blood, a marker for the activity of myeloma cells.

What is the Urine protein electrophoresis (UPEP) test?

This test measures specific proteins in the urine. The test separates proteins in the urine based on their electrical charge. The urine protein electrophoresis test is often used to find abnormal substances such as the M proteins.

What is multiple myeloma?

Myeloma is a cancer of plasma cells, a type of white blood cell (WBC) in the bone marrow that is responsible for making immunoglobulins. In Greek, the language of most medical terms, “myelo” refers to the blood-producing cells in the bone marrow, and “oma” refers to a tumor or mass of cancer cells. A malignant plasma cell is called a myeloma cell.

Myeloma most often grows in the marrow within the bones of the spine, skull, pelvis, rib cage, shoulders, and hips. Usually, the bones of the hands, feet, and lower parts of the arms and legs are not affected, preserving the function of these critical areas.

MGUS, SMM, and active myeloma:

The earliest stage of myeloma is not cancer at all, but is a benign condition called MGUS, the presence of a low level of monoclonal protein (M-protein) without any indicators of active myeloma. People with MGUS are monitored carefully to make sure the diagnosis is correct and there is no change in their status. As time goes by, if the level of M-protein remains stable and there are no other health changes, the time between visits to the hematologist can be extended. All myeloma patients have MGUS before they progress to active myeloma, but only 20% of people diagnosed with MGUS eventually get myeloma.

The risk of progression from MGUS to myeloma is 1% per year.

The stage of myeloma between MGUS and active myeloma is called smoldering multiple myeloma (SMM), which is characterized by a higher level of M-protein than MGUS but with no indicators of active myeloma. The risk of progression to active myeloma among patients with standard-risk SMM is 10% per year for the first five years, 3% per year for the next five years, and 1%–2% per year for the next 10 years.

Basic definitions:

References:

- Glavey SV, et al. Monoclonal gammopathy: The good, the bad and the ugly. Blood Reviews. In press. http://dx.doi.org/10.1016/j.blre.2015.12.001.

- Rajkumar SV. Diagnosis of monoclonal gammopathy of undetermined significance. http://www.uptodate.com/home.

- International Myeloma Foundation: https://www.myeloma.org/what-is-multiple-myeloma