What is monoclonal gammopathy of undetermined significance (MGUS)?

Updated: Sep 07, 2018
  • Author: Suzanne R Fanning, DO; Chief Editor: Emmanuel C Besa, MD  more...
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Answer

Monoclonal gammopathy of undetermined significance (MGUS) is the most common of a spectrum of diseases called plasma cell dyscrasias. The term MGUS denotes the presence of a monoclonal immunoglobulin (Ig), also called an M-protein, in the serum or urine in persons without evidence of multiple myeloma (MM), Waldenström macroglobulinemia (WM), amyloidosis (AL) or other lymphoproliferative disorders. [1]

Immunoglobulin involvement may be IgM, non-IgM (ie, IgA, IgG, or, rarely, IgD or IgE), or light chain. [2] All pose a risk, albeit varying, of progression to a malignant disorder. Typically, IgG and IgA MGUS progress to MM, IgM MGUS progresses to WM or other lymphoproliferative disorders, and light-chain MGUS is the precursor of light-chain MM. [3]

The cause of MGUS is unknown, though the same theories that apply to the pathogenesis of MM may be valid in MGUS. MM is almost always preceded by MGUS. [3]

Distinguishing between MM and MGUS is critical because patients with MGUS are conservatively treated and do not need chemotherapy. In contrast, MM is a uniformly lethal disease that does not need therapy in its initial stages but progresses to an advanced or aggressive stage that requires therapy.


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