II. Epidemiology
- Ultimately responsible for 20% of Multiple Myeloma cases after progression
- Age
- Present in 2-3% of patients over age 50 years (increases to 5% in age over 70 years old)
- Gender
- More common in men
- Race and ethnicity
- More common in black patients than white patients
III. Evaluation: Factors suggesting higher risk of Multiple Myeloma progression
- Criteria
- Elevated M Protein Level 1.5 to 3 g/dl (levels >3 g/dl consistent with Multiple Myeloma)
- Non-IgG MGUS
- Abnormal free light chain ratio
- Distinguishing features from Multiple Myeloma
- Bone Marrow plasma cells <10%
- Asymptomatic with no end-organ damage (see CRAB Criteria in Monoclonal Gammopathy)
- Interpretation
- Risk of Multiple Myeloma is 58% in 20 years if all 3 factors present
IV. Associated Conditions: MGUS Progression to other Plasma Cell Disorders
- Multiple Myeloma (RR 23.9)
- Immunoglobulin Light Chain Amyloidosis (RR 8.8)
- Macroglobulinema (RR 47.6)
- Plasmacytoma (RR 12.7)
V. Monitoring
- Low risk of progression (5% risk of progression)
- Intermediate risk of progression (21-37% risk of progression)
- Criteria (1-2 risk factors present)
- M-Spike >1.5 g/L OR
- Non-IgG type OR
- Free light chain ratio abnormal (involved to uninvolved >100)
- Evaluation and Management
- Hematology referral
- Bone Marrow Biopsy
- Bone imaging
- Repeat SPEP in 6 months and then every year indefinately
- Criteria (1-2 risk factors present)
- High risk of progression (58% risk of progression)
- Criteria (all 3 risk factors present)
- M-Spike >1.5 g/L AND
- Non-IgG type AND
- Free light chain ratio abnormal (involved to uninvolved >100)
- Evaluation and Management
- Hematology referral
- Bone Marrow Biopsy
- Bone imaging
- Repeat SPEP in 6 months and then every year indefinately
- Criteria (all 3 risk factors present)
VI. Course
- Progresses to Multiple Myeloma in 1% of cases per year
VII. References
- Thompson (2017) Monoclonal Gammopathy, Mayo Clinical Reviews, Rochester, MN