Monoclonal gammopathies of undetermined significance: a review

Authors

  • Robert A. Kyle,

    Corresponding author
    1. Division of Hematology and Internal Medicine, Mayo Clinic, Rochester, MN, USA.
      Robert A. Kyle, MD
      Division of Hematology and Internal Medicine
      Mayo Clinic
      200 First Street SW
      Rochester, MN 55905
      USA
      e-mail: kyle.robert@mayo.edu
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  • S. Vincent Rajkumar

    1. Division of Hematology and Internal Medicine, Mayo Clinic, Rochester, MN, USA.
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Robert A. Kyle, MD
Division of Hematology and Internal Medicine
Mayo Clinic
200 First Street SW
Rochester, MN 55905
USA
e-mail: kyle.robert@mayo.edu

Abstract

Summary:  Monoclonal gammopathy of undetermined significance (MGUS) denotes the presence of a monoclonal protein (M-protein) in patients without evidence of multiple myeloma (MM), macroglobulinemia, amyloidosis (AL), or a related plasma cell proliferative disorder. MGUS is found in approximately 3% of persons older than 70 years and in about 1% of those older than 50 years. In a series of 1384 patients from south-eastern Minnesota in whom MGUS was diagnosed at Mayo Clinic from 1960 through 1994, the risk of progression was 1% per year. Patients were at risk of progression even after 25 years or more of a stable monoclonal gammopathy. The risk of development of MM was increased by 25-fold, the risk of macroglobulinemia was 46-fold, and the risk of primary AL was 8.4-fold when compared with a similar population (Surveillance, Epidemiology and End Results). The concentration of the serum M-protein was the major independent predictor of progression. Patients with an immunoglobulin M (IgM) or an IgA monoclonal gammopathy had a higher risk of progression than those with an IgG monoclonal gammopathy. The presence of a urine M-protein or the reduction of one or more uninvolved Igs was not a risk factor for progression. MGUS may be associated with many different disorders, including lymphoproliferative diseases, leukemia, connective tissue disorders, dermatologic diseases, and neurologic disorders.

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