From the Guidelines
Monoclonal gammopathy of unknown significance (MGUS) is a benign condition characterized by the presence of an abnormal protein (M protein) in the blood, affecting approximately 3.5% of the population over 50 years of age, with an average risk of progression to multiple myeloma or other lymphoproliferative disorders of 1% per year.
Definition and Diagnosis
MGUS is defined by a M-protein less than 30 g/L, bone marrow plasma cell percentage less than 10%, and absence of signs or symptoms related to multiple myeloma or other lymphoproliferative malignancies 1. The condition is diagnosed through blood tests and bone marrow biopsies.
Types of MGUS
There are different types of MGUS, including IgG, IgA, and IgM MGUS, each with its own set of diagnostic criteria 1. Light-chain MGUS is another type, defined by an abnormal κ/λ free light-chain ratio and increase in concentration of the involved light-chain 1.
Monitoring and Management
Patients with MGUS should undergo regular monitoring with blood tests every 6-12 months to check for potential progression 1. Risk factors for progression include higher M protein levels, abnormal free light chain ratios, and non-IgG type M proteins. While MGUS itself causes no symptoms, it's essential to monitor for signs of progression such as bone pain, unexplained fatigue, frequent infections, or kidney problems.
Key Considerations
- MGUS affects approximately 3.5% of the population over 50 years of age 1
- The average risk of progression to multiple myeloma or other lymphoproliferative disorders is 1% per year 1
- Regular monitoring with blood tests every 6-12 months is recommended 1
- Risk factors for progression include higher M protein levels, abnormal free light chain ratios, and non-IgG type M proteins 1
From the Research
Definition and Overview
- Monoclonal gammopathy of unknown significance (MGUS) is a premalignant plasma cell dyscrasia that consistently precedes multiple myeloma (MM) with a 1% risk of progression per year 2.
- MGUS is defined by the absence of end-organ damage or symptoms, a small amount of monoclonal immunoglobulin (M protein), and low volume of plasma cells 3.
- It is a common incidental finding, detected at high frequency in a variety of disciplines, and can be associated with non-malignant diseases or be a precursor of malignant lymphoproliferative disorders 4.
Risk of Progression
- The risk of progression to malignant disease ranges from 0.5% to 1% per year, meaning most patients have indolent disease 3.
- Patients with MGUS can be risk-stratified on the basis of the amount and type of their monoclonal protein as well as whether they have an abnormal light-chain ratio 5.
- There are three subtypes with different rates and types of progression: IgM-MGUS, non-IgM-MGUS, and light-chain MGUS 4.
Diagnosis and Management
- Screening is performed by serum protein electrophoresis, immunofixation, and determination of quantitative immunoglobulins and free light chains in serum 4.
- Guideline-concordant management of MGUS is determined by predicted risk of progression to malignant disease, which depends on subtype of immunoglobulin, M protein concentration, and free light chain ratio 3.
- Patients with low-risk MGUS can safely defer bone marrow biopsy and advanced imaging, and should undergo periodic laboratory monitoring, while intermediate- and high-risk MGUS should trigger bone marrow biopsy and bone imaging to detect overt MM and shorter monitoring intervals 3.