Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma-cell proliferative disorder characterized by the presence of a monoclonal immunoglobulin and associated with a life-long average 1% annual risk of developing lymphoproliferative malignancies. The prevalence of MGUS is about 3% in the general population 50 years of age or older. The current diagnostic criteria for MGUS are concentration of monoclonal protein in serum less that 3.0 g/dL, bone marrow plasmacytosis less that 10% and lack of organ damage including hypercalcaemia, renal impairment, anemia and bone lesions. Currently, there are no methods for classification of patients due to the risk of progression to MM, and there is no therapy to prevent the progression, so the standard treatment for patients with MGUS is observation. The increased risk of developing MGUS among first-degree relatives of MGUS patients is observed, however, due to the low absolute risk for MGUS and the lack of available intervention and early disease therapies, familial screening for MGUS is not recommended.