[Monoclonal gammopathy of undetermined significance and monoclonal B-lymphocytosis].

Monoclonal gammopathy of undetermined significance (MGUS) and monoclonal B lymphocytosis (MBL) are asymptomatic premalignant conditions which can progress to a symptomatic disease state requiring therapy. Considering the high prevalence rate of these disorders, precursor patients are often diagnosed during routine clinical examinations. Only a minor portion of cases progress to overt malignancies, which raises the question of how to identify patients with the probability of progression. In recent years improvements in the understanding of the pathogenesis of both disorders led to the development of risk models and the estimation of the individual risk of progression. The definition of high-risk and low-risk patients allows a tailored clinical management. This report provides information on the biology, risk stratification, diagnosis, and follow-up of patients with MGUS and MBL.