A Comprehensive Review of Monoclonal Gammopathy of Undetermined Significance

Monoclonal gammopathy of undetermined significance (MGUS) is characterized as a nonmalignant or premalignant state whereby monoclonal immunoglobulins are detected in plasma, urine, or both. Approximately 3% to 4% of the population over the age of 50 is diagnosed with MGUS. It is estimated that 1% will progress to multiple myeloma or lymphoma over 20 years and therefore require ongoing clinical monitoring. Monoclonal gammopathy of undetermined significance is categorized into three types that are determined by the paraprotein clone: immunoglobulin M (IgM) MGUS, non-IgM MGUS, and light chain MGUS. There are high-risk genetic, biochemical, and clinical factors that increase the risk of transformation to multiple myeloma or lymphoma. The incidence of MGUS is two- to threefold higher in the Black population compared with the White population, along with an earlier age of onset. Familial risk and modifiable lifestyle factors are also associated with the development of MGUS and multiple myeloma. Certain monoclonal gammopathies, known as monoclonal gammopathy of clinical significance (MGCS), are associated with various organs that are involved (kidney, brain, skin, lungs, liver, eyes, and heart). The most common MGCS are associated with renal and neurological abnormalities, and treatment may be considered. Early diagnosis and multidisciplinary approaches to mitigate organ damage and other complications are important for the recognition and management of MGCS. Monoclonal gammopathy of undetermined significance is monitored rather than treated unless there are clinical findings of progression or organ dysfunction. Ongoing research and clinical trials are essential to refine monitoring guidelines, develop targeted therapies, and explore preventive measures aimed at reducing progression to multiple myeloma and other malignancies.