Monoclonal gammopathy of undetermined significance

Case history

An otherwise healthy 49-year-old black man presents with a second sinusitis infection in 4 months. He has no significant medical history or current medications, and has no back pain or gastrointestinal or urinary symptoms. Physical examination is unremarkable. Splenomegaly and lymphadenopathy are absent, and cardiovascular and respiratory examinations are normal. Routine laboratory results show a normal full blood count, normal kidney and liver function, absent protein in the urine, and mildly increased total protein in serum chemistries. Serum protein electrophoresis shows an IgG monoclonal (M) protein of 20 g/L (2 g/dL).