Monoclonal gammopathy of undetermined significance

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What is monoclonal gammopathy of undetermined significance and whom does it affect?

Plasma cells produce immunoglobulins (Ig), or antibodies, substances that circulate in the blood to defend the body by attacking any foreign substances that enter the organism. Each Ig has two heavy chains: gamma (IgG), alfa (IgA), mu (IgM), delta (IgD), or epsilon (IgE), and two light chains (kappa or delta).

Monoclonal gammopathies include a group of diseases characterised by the clonal proliferation of plasma cells that produce a single type of light and/or heavy chain (monoclonal component) in excessive quantities.

The term monoclonal gammopathy of undetermined significance (MGUS) is used when a monoclonal component is present but the diagnostic criteria are lacking to diagnose multiple myeloma, primary amyloidosis, Waldenström macroglobulinemia or heavy chain disease. Monoclonal gammopathy may also be referred to as idiopathic gammopathy.

MGUS has a considerable prevalence amongst those of advanced age, being observed in 1% of people over the age of 60 and more than 5% in those over 80 years of age.

Symptoms and diagnosis

In most cases (60-70%) MGUS is detected by chance as a result of a routine blood test.

Diagnosis is based on the presence of monoclonal immunoglobulins in quantities lower than 30 g/L and a percentage of bone marrow plasma cells lower than 10%, with the absence of organic injury attributable to the gammopathy (renal, bone, etc.).


All MGUS patients must be monitored and undergo regular checks. It is important to establish the differential diagnosis between MGUS and multiple myeloma since MGUS does not require treatment, whereas multiple myeloma generally does.


According to various studies, 12%, 25% and 30% of MGUS patients develop multiple myeloma after 10, 20 and 25 years respectively. The only way to establish whether MGUS is really benign, or if it constitutes the first manifestation of multiple myeloma is to undertake an annual test of the M component (anomalous monoclonal antibody).

Links of interest concerning medical issues relating to MGUS

For more quality information about MGUS, you can consult the following websites:

Help and support

On our website you will also find the testimonies of people who are suffering, or who have suffered, from this disease. We would also like to invite you to follow us on our main social networks (FacebookTwitter e Instagram) where we often share patients' accounts of overcoming the disease.

If you are resident in Spain, you can also contact us via email so that we can help put you in contact with other patients who have overcome this disease.

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Webpage updated 01/09/2023 12:58:16