Monoclonal gammopathy of undetermined significance (MGUS)

Last updated: Friday, 06, August, 2010
Key InformationAppropriate Tests

MGUS refers to the presence of a paraprotein without symptoms or evidence of multiple myeloma. In monoclonal gammopathy of undetermined significance (MGUS) the paraprotein 50 years of age. The risk of progression to myeloma is 12% and 25% at 10 and 20 years respectively. Immune paresis (reduction in normal immunoglobulins) and small amounts of light chain in the urine do not increase the risk of progression to myeloma.

FBC, blood film; ESR; protein (total) and protein electrophoresis with paraprotein quantitation, paraprotein typing, immunoglobulins G, A, M; beta-2-microglobulin. Urine protein, Bence Jones protein.Bone marrow aspiration and trephine biopsy.

A bone marrow biopsy is usually not required in patients with small (<10 g/L) paraproteins and no other features to suggest multiple myeloma. On immunophenotyping, the plasma cells in MGUS typically express CD19 and do not express CD56, with the converse applying to plasma cells in myeloma.


Patients with MGUS should be observed with clinical review, full blood count, electrolytes, serum calcium, serum EPG, immunofixation, urine for Bence Jones protein and quantitative immunoglobulins every 3-12 months, depending on the age and level of concern in the individual patient.

See Paraproteinaemia and Multiple myeloma.