Overview

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.

This abnormal protein is formed within your bone marrow, the soft, blood-producing tissue that fills in the center of most of your bones. The disorder occurs most commonly in older men.

MGUS usually causes no problems. But sometimes it can progress to more-serious diseases, including some forms of blood cancer.

If you have high amounts of this protein in your blood, it's important to have regular checkups so that you can get earlier treatment if it does progress. If there's no disease progression, MGUS doesn't require treatment.