Monoclonal Gammopathy of Undetermined Significance (MGUS)Monoclonal Gammopathy of Undetermined Significance (MGUS).

Abstract

Monoclonal gammopathy of undetermined significance (MGUS) is one of the most prevalent premalignant conditions associated with a risk of malignant transformation to multiple myeloma (MM) or other forms of lymphoproliferative disorders with risk of progression of approximately 1% per year. IgG and IgA MGUS are precursor conditions of multiple myeloma (MM), whereas light-chain MGUS is a precursor condition of light chain MM. IgM MGUS is a precursor condition of Waldenström macroglobulinemia (MW) or other lymphoproliferative diseases. Assessment of the risk of progression of patients with asymptomatic monoclonal gammopathies (MG) is based on various factors, including the serum paraprotein (M protein) concentration, isotype of M protein, serum free light chain ratio, infiltration of bone marrow plasmocytes, reduction of one or two noninvolved immunoglobulin subtype levels (immunoparesis), evolving and non-evolving subtype of MGUS, ratio of normal/abnormal plasma cells in bone marrow identified by multiparametric flow cytometry techniques and number of circulating plasma cells in peripheral blood. Three risk stratification models have been constructed that are useful in daily practice for predicting risk of progression of MGUS into malignant forms of monoclonal gammopathy - MAYO, PETHEMA and CMG model. The goal of all three models is to identify correctly prognostic markers that can divide patients into low-risk MGUS and high-risk MGUS groups. This review provides a look at the definition, pathogenesis, diagnostic algorithm, clinical significance and stratification of MGUS patients, followed by recommendations for patient risk dispensarisation intervals.