Management of Monoclonal Gammopathy of Undetermined Significance (MGUS) with Leukopenia

Evaluation and Diagnosis

A comprehensive evaluation should include a complete blood count with differential, calcium, creatinine, and serum protein electrophoresis with immunofixation, as recommended by the International Myeloma Society 1, 2
Analysis of serum free light chains is essential for evaluating the risk of progression, with a strength of evidence level of II 2, 3
Leukopenia should be characterized (neutropenia, lymphopenia, or pancytopenia) to guide further evaluation 4
Tests for autoimmune diseases associated with MGUS, such as the Coombs test, should be considered, as MGUS can be associated with autoimmune cytopenias 5, 4

The Mayo Clinic risk stratification model should be used to evaluate the risk of progression to multiple myeloma or related disorders 2, 3
Low-risk: IgG isotype, M protein <15 g/L, and normal free light chain ratio (risk of progression 5% at 20 years) 1, 2
Intermediate-low risk: one risk factor present (risk of 21% at 20 years) 2
Intermediate-high risk: two risk factors present (risk of 37% at 20 years) 2
High-risk: three risk factors present (risk of 58% at 20 years) 2

Follow-up should be personalized based on risk stratification and life expectancy 1, 2
Low-risk MGUS: initial follow-up at 6 months, then every 1-2 years if stable 1, 2
Non-low-risk MGUS and light-chain MGUS: initial follow-up at 6 months, then annually 1, 2
All types of MGUS with life expectancy <5 years: no systematic follow-up, but additional investigations if symptoms suggestive of progression 1, 7

If leukopenia is related to MGUS (autoimmune mechanism), treatment depends on severity 5
Mild leukopenia without complications may require only surveillance 5
Severe or symptomatic leukopenia may require treatment targeting the MGUS clone 5
Treatment targeting the MGUS clone should only be considered in cases of aggressive and disabling disease, and only when there is a clear causal relationship between MGUS and the associated disorder 5

There is currently no intervention to prevent or delay the progression of MGUS, and any intervention approach should only be done in the context of a clinical trial 1, 2
Screening of the general population for MGUS is not recommended outside of research studies 2