Merck Manual

Please confirm that you are a health care professional

honeypot link

Monoclonal Gammopathy of Undetermined Significance (MGUS)

By

James R. Berenson

, MD, Institute for Myeloma and Bone Cancer Research

Last full review/revision Sep 2019| Content last modified Sep 2019
Click here for Patient Education

Monoclonal gammopathy of undetermined significance (MGUS) is the production of M-protein by noncancerous plasma cells in the absence of other manifestations typical of multiple myeloma.

The incidence of monoclonal gammopathy of undetermined significance (MGUS) increases with age, from 1% of people aged 25 years to > 5% of people > 70 years. MGUS may occur in association with other disorders (see table Classification of Plasma Cell Disorders Classification of Plasma Cell Disorders Plasma cell disorders are a diverse group of disorders of unknown etiology characterized by Disproportionate proliferation of a single clone of B cells Presence of a structurally and electrophoretically... read more ), in which case M-proteins (monoclonal immunoglobulin proteins, which may consist of both heavy and light chains or of only a light chain) may be antibodies produced in large amounts in response to protracted antigenic stimuli.

Diagnosis of MGUS is usually suspected when M-protein is incidentally detected in blood or urine during a routine examination. On laboratory evaluation, M-protein is present in low levels in serum (< 3 g/dL) or urine (< 200 mg/24 hours). MGUS is differentiated from malignant plasma cell disorders because M-protein levels are lower and lytic bone lesions, anemia, and renal dysfunction are absent. Because of fracture risk, baseline evaluation with a skeletal survey (ie, plain x-rays of skull, long bones, spine, pelvis, and ribs) and bone densitometry should be done. Bone marrow shows only mild plasmacytosis (< 10% of nucleated cells).

No antineoplastic treatment is recommended. However, recent studies suggest that MGUS patients with associated bone loss (osteopenia or osteoporosis Osteoporosis Osteoporosis is a progressive metabolic bone disease that decreases bone mineral density (bone mass per unit volume), with deterioration of bone structure. Skeletal weakness leads to fractures... read more Osteoporosis ) may benefit from treatment with intravenous bisphosphonates but less frequently than the monthly treatments usually required to treat patients with multiple myeloma Multiple Myeloma Multiple myeloma is a cancer of plasma cells that produce monoclonal immunoglobulin and invade and destroy adjacent bone tissue. Common manifestations include lytic lesions in bones causing... read more Multiple Myeloma . Every 6 to 12 months, patients should undergo clinical examination and serum and urine protein electrophoresis to evaluate for disease progression.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read
Test your knowledge
Overview of Thrombotic Disorders
Thrombotic disorders can be caused by genetic defects, which increase the risk of venous thromboembolism, or acquired defects, which increase the risk of arterial and venous thrombosis. Of the acquired causes, which of the following is most likely to increase a patient’s risk of venous thrombosis?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP