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Monoclonal Gammopathy of Undetermined Significance

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Monoclonal Gammopathy of Undetermined Significance, MGUS

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