MGUS (Monoclonal Gammopathy of Uncertain Significance)

Monoclonal gammopathy of uncertain significance (MGUS), sometimes called monoclonal gammopathy of unknown or undetermined significance, is a relatively benign condition that can lead to multiple myeloma. The risk of a patient with MGUS developing myeloma is approximately 1% per year. Like multiple myeloma, MGUS is characterized by an excess of M protein—an abnormal antibody produced by plasma cells. In the case of MGUS, however, symptoms are typically absent and the plasma cells do not form tumors or lesions.

While there generally are no physical symptoms, diagnostic testing can reveal certain characteristics of MGUS:

  • Detectable low-level M protein levels in the blood or urine
  • Low percentage of plasma cells in the bone marrow
  • Absence of anemia, renal failure, hypercalcemia, or bone lesions

Risk factors for MGUS are the same for multiple myeloma and complications are generally associated with the development of more serious disorders, such as multiple myeloma and other cancers like lymphoma.