Monoclonal Gammopathy of Undetermined Significance

The presence of M protein in the serum or urine of asymptomatic, apparently healthy persons.

Monoclonal gammopathy of undetermined significance--usually a benign disorder--is a likely diagnosis in a patient with elevated serum levels of monoclonal protein but with no other symptoms and neither osteolytic lesions nor plasma cell infiltration. Confirming findings for this diagnosis include no significant amounts (ie, < 60 mg/24 hours) of a single type of light chain (ie, Bence Jones protein) in the urine and serum levels of monoclonal protein < 2 g/dL.

Only time will determine if a diagnosis of monoclonal gammopathy of undetermined significance is really early multiple myeloma. Over 20 years, about 25% of patients initially diagnosed with monoclonal gammopathy develop overt multiple myeloma or other lymphoproliferative lesions. No evidence indicates that not treating these patients is harmful.