Monoclonal gammopathy of undetermined significance (MGUS) is, in many ways, a unique hematologic entity. Unlike most hematologic conditions in which the diagnosis is intentional and credited to hematologists, the discovery of MGUS is most often incidental and made by nonhematologists. MGUS is considered an obligate precursor to several lymphoplasmacytic malignancies, including immunoglobulin light-chain amyloidosis, multiple myeloma, and Waldenström macroglobulinemia. Therefore, long-term follow-up is generally recommended. Despite its high prevalence, there is surprisingly limited evidence to inform best clinical practice both at the time of diagnosis and during follow-up. We present 7 vignettes to illustrate common clinical management questions that arise during the course of MGUS. Where evidence is present, we provide a concise summary of the literature and clear recommendations on management. Where evidence is lacking, we describe how we practice and provide a rationale for our approach. We also discuss the potential harms associated with MGUS diagnosis, a topic that is rarely, if ever, broached between patients and providers, or even considered in academic debate.
© 2018 by The American Society of Hematology.