Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which an abnormal protein — known as monoclonal protein or M protein — is in your blood. The protein is produced in a type of white blood cell (plasma cells) in your bone marrow.
MGUS usually causes no problems. But sometimes it can progress over years to other disorders, including some forms of blood cancer.
It's important to have regular checkups to closely monitor monoclonal gammopathy so that if it does progress, you get earlier treatment. If there's no disease progression, MGUS doesn't require treatment.
Monoclonal gammopathy of undetermined significance (MGUS) care at Mayo Clinic