Asymptomatic pre-malignant disorder associated with relatively low risk (on average 0.5% to 1.0% per year) of progression to multiple myeloma or related plasma cell proliferative malignancies.
No aetiological risk factors have been defined. Male sex, older age, family history of monoclonal gammopathy of undetermined significance, African ancestry, and exposure to radiation or pesticide are associated with a higher prevalence.
There is no indication for specific treatment. Clinical- and laboratory-based follow up is recommended.
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.
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
- male sex
- age >50 years
- African ancestry
- family history of MGUS or multiple myeloma
- immune-mediated conditions
- radiation exposure
- pesticide exposure
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
Shaji Kumar, MD
Professor of Medicine
Division of Hematology
SK has served as a consultant for Janssen, Abbvie, Amgen, Merck, Celgene, Takeda, and Skyline.
Professor Shaji Kumar would like to gratefully acknowledge Dr Ola Landgren, a previous contributor to this topic. OL is an author of several references cited in this topic.
Daniel Catovsky, MD
Section of Haemato-Oncology
Brookes Lawley Institute of Cancer
DC declares that he has no competing interests.
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