Monoclonal Gammopathy of Undetermined Significance

A premalignant plasma cell disorder characterized by the presence of a monoclonal (M) protein in serum without evidence of multiple myeloma, other plasma cell malignancy, or related organ damage (no CRAB features: hyperCalcemia, Renal impairment, Anemia, Bone lesions).
Diagnostic thresholds: M-protein <3 g/dL, clonal plasma cells <10% in bone marrow, and no myeloma-defining events.
Risk: Progresses to multiple myeloma or related disorders at ~1% per year.
Management: No treatment; requires long-term monitoring for progression.
For you as an oncology pharmacist: MGUS doesn’t require therapy, but recognizing it is critical to avoid unnecessary treatment and to counsel patients on the importance of surveillance.