benign monoclonal gammopathy

https://doi.org/10.1351/goldbook.12948
Nonmalignant overproduction of $\ce{\upgamma\!\mbox{-}globulin}$ by a single clone of lymphocytes.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1134 [Terms] [Paper]