Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which a person has moderately elevated levels of an abnormal immunoglobulin protein called M protein in the blood.
As in multiple myeloma, MGUS is a disease that begins in the plasma cells, the white blood cells that produce antibodies to fight infections. M protein is produced by the plasma cells. However, this change in the blood does not result in any symptoms.
MGUS can be precancerous in the sense that, even after many years of remaining stable, it may progress to multiple myeloma. However, this occurs in a very small percentage of patients. Most patients with MGUS remain well for many years without treatment.
If you have MGUS, you should have your protein levels monitored through regular blood testing because of the slight risk of progression to multiple myeloma. This can typically be done by your primary care doctor under the guidance of physicians at Memorial Sloan Kettering.