Print OverviewMonoclonal gammopathy of undetermined significance (MGUS) is a condition in which an atypical protein is found in the blood. The protein is called monoclonal protein or M protein. This protein is made in the soft, blood-producing tissue in the center of bones. This blood-producing tissue is bone marrow. Monoclonal gammopathy of undetermined significance occurs most often in older men. MGUS usually causes no problems. But sometimes it can lead to more-serious diseases. These include some forms of blood cancer. People who have high amounts of this protein in the blood need regular checkups. That's so they can get earlier treatment if the condition gets worse. If it doesn't get worse, MGUS doesn't need treatment.Products & ServicesA Book: Mayo Clinic Family Health BookNewsletter: Mayo Clinic Health Letter — Digital EditionShow more products from Mayo Clinic SymptomsPeople with monoclonal gammopathy often don't have symptoms. Some people have a rash or nerve problems, such as numbness or tingling. A blood test for another condition might find MGUS by chance. Request an appointment CausesExperts don't know what causes MGUS. Changes in genes and being around certain chemicals, such as those used to kill pests, appear to play a role. Risk factorsFactors that increase your risk of developing MGUS include: Age. The average age at diagnosis is 70 years. Race. Africans and Black Americans are more likely to get MGUS than white people are. Sex. MGUS is more common in men. Family history. Having family members with MGUS might increase the risk. ComplicationsEach year, about 1% of people with MGUS get certain types of blood cancers or other serious diseases, such as: Multiple myeloma. Light chain amyloidosis. Waldenstrom macroglobulinemia. Lymphoma. Other issues linked to MGUS include broken bones, blood clots, kidney problems, and damage to nerves outside of the brain and spinal cord, also known as peripheral neuropathy. By Mayo Clinic Staff Monoclonal gammopathy of undetermined significance (MGUS) care at Mayo Clinic Request an appointment Diagnosis & treatment Aug. 01, 2023 Print Show references Goldman L, et al., eds. Plasma cell disorders. In: Goldman-Cecil Medicine. 26th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Jan. 6, 2023. Ferri FF. Monoclonal gammopathy of undetermined significance (MGUS). In: Ferri's Clinical Advisor 2023. Elsevier; 2023. https://www.clinicalkey.com. Accessed Jan. 6, 2023. Monoclonal gammopathy of undetermined significance (MGUS). Merck Manual Professional Version. https://www.merckmanuals.com/professional/hematology-and-oncology/plasma-cell-disorders/monoclonal-gammopathy-of-undetermined-significance-mgus?query=mgus#. Accessed April 6, 2023. Laubach JP. Diagnosis of monoclonal gammopathy of undetermined significance. https://www.uptodate.com/contents/search. Accessed Jan. 6, 2023. Rajhumar SV. Clinical course and management of monoclonal gammopathy of undetermined significance. https://www.uptodate.com/contents/search. Accessed Jan. 6, 2023. AskMayoExpert. Monoclonal gammopathy of undetermined significance (MGUS) (adult). Mayo Clinic; 2021. Ami TR. Allscripts EPSi. Mayo Clinic. Feb. 1, 2023. Pruthi RK (expert opinion). Mayo Clinic. April 26, 2019. Related Associated Procedures Bone marrow biopsy Complete blood count (CBC) Creatinine test X-ray Show more associated procedures Products & Services A Book: Mayo Clinic Family Health Book Newsletter: Mayo Clinic Health Letter — Digital Edition Show more products and services from Mayo Clinic Monoclonal gammopathy of undetermined significance (MGUS)Symptoms&causesDiagnosis&treatmentDoctors&departmentsCare atMayoClinic Advertisement Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. Advertising & Sponsorship Policy Opportunities Ad Choices Mayo Clinic Press Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press. Mayo Clinic on Incontinence - Mayo Clinic PressMayo Clinic on IncontinenceThe Essential Diabetes Book - Mayo Clinic PressThe Essential Diabetes BookMayo Clinic on Hearing and Balance - Mayo Clinic PressMayo Clinic on Hearing and BalanceFREE Mayo Clinic Diet Assessment - Mayo Clinic PressFREE Mayo Clinic Diet AssessmentMayo Clinic Health Letter - FREE book - Mayo Clinic PressMayo Clinic Health Letter - FREE book CON-20166978 Patient Care & Health Information Diseases & Conditions Monoclonal gammopathy of undetermined significance (MGUS)