Monoclonal gammopathy of undetermined significance

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.[1]Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncol. 2014;15:e538-e548. http://www.ncbi.nlm.nih.gov/pubmed/25439696?tool=bestpractice.com

[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].