Summary
Definition
Monoclonal gammopathy of undetermined significance (MGUS) is an asymptomatic disorder associated with an increased risk of developing multiple myeloma and related plasma cell proliferative malignancies. The following criteria must be met for diagnosis: presence of a monoclonal (M) protein in the serum (at a concentration <30 g/L [3 g/dL]) or in urine (<500 mg per 24 hours); <10% plasma cells in the bone marrow (a bone marrow examination is only required if M protein is >15 g/L [1.5 g/dL], or for non-IgG MGUS, or if the free light chain ratio is abnormal); and an absence of lytic bone lesions, anaemia, hypercalcaemia, renal insufficiency, or amyloidosis related to the plasma cell proliferative process.[1]
[Figure caption and citation for the preceding image starts]: Haematoxylin-eosin section of bone marrow biopsy showing mild increase in plasma cellsFrom the collection of Ola Landgren, MD, PhD [Citation ends].
[Figure caption and citation for the preceding image starts]: CD138 immuno-histochemical staining highlighting small clusters of plasma cellsFrom the collection of Ola Landgren, MD, PhD [Citation ends].
History and exam
Key diagnostic factors
- at-risk demographic (male, age >50 years, African ancestry)
- clinically asymptomatic
- positive family history
- history of radiation exposure
- history of pesticide exposure
Other diagnostic factors
- history of immunosuppression or infections
- presence of peripheral neuropathy
Risk factors
- male sex
- age >50 years
- African ancestry
- family history of MGUS or multiple myeloma
- immune-mediated conditions
- radiation exposure
- pesticide exposure
Diagnostic investigations
1st investigations to order
- electrophoresis with immunofixation and measurement of serum immunoglobulins
- FBC with differential
- serum calcium
- serum creatinine
- urinalysis and 24-hour urine collection with electrophoresis and immunofixation
- serum free light chains assay
- metastatic bone survey (conventional x-ray or whole body low-dose CT scan)
Investigations to consider
- bone marrow aspiration and/or biopsy
- bone mineral density scan
- MRI scan
- PET scan
Treatment algorithm
Contributors
Authors
Shaji Kumar, MD
Professor of Medicine
Division of Hematology
Mayo Clinic
Rochester
MN
Disclosures
SK has received research funding for clinical trials to the institution from Abbvie, Amgen, Allogene, Astra-Zeneca, BMS, Carsgen, GSK, Janssen, Novartis, Roche-Genentech, Takeda and Regeneron. SK has participated in consulting and advisory board activities (with no personal payments) for Abbvie, Amgen, BMS, Janssen, Roche-Genentech, Takeda, Astra-Zeneca, Bluebird Bio, Secura Biotherapeutics, Trillium, Loxo Oncology, K36, Sanofi, ArcellX, and (with personal payment) Oncopeptides, Beigene and Antengene.
Acknowledgements
Professor Shaji Kumar would like to gratefully acknowledge Dr Ola Landgren, a previous contributor to this topic.
Disclosures
OL is an author of several references cited in this topic.
Peer reviewers
Daniel Catovsky, MD
Consultant Haemato-Oncologist
Section of Haemato-Oncology
Brookes Lawley Institute of Cancer
Sutton
UK
Disclosures
DC declares that he has no competing interests.
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