Monoclonal gammopathy of undetermined significance and smoldering myeloma: new insights into pathophysiology and epidemiology.

Routine screening for monoclonal gammopathy of undetermined significance (MGUS) is not indicated. Despite this fact, MGUS is a common finding in medical practice. Almost all individuals diagnosed with MGUS represent incidental cases diagnosed when physicians order serum protein electrophoresis, immunofixation, or both, as part of the work-up of a number of common symptoms and laboratory abnormalities. In the absence of reliable molecular predictors of outcome, the detection of an early precursor state typically imposes a complex situation for the patient and the responsible physician-usually, it leads to a lot of questions that lack clear answers. In the past years, several novel insights have been gained in the area of multiple myeloma (MM) precursor disease. This review focuses on results from recent investigations and discusses implications for diagnostic work-up, clinical management, and patient counseling. More specifically, it sheds light on the following commonly asked questions by patients and physicians: i) what is the risk of progression from precursor to full-blown MM, and are there ways to risk-stratify patients?; ii) is MM always preceded by a precursor state, and is there anything that could or should be done to delay or prevent progression?; and iii) why do some individuals develop MM precursor diseases, and is there a reason to screen the family?