Malcolm L. Brigden, MD INVESTIGATION AND MANAGEMENT OF THE PATIENT WITH A MONOCLONAL PROTEIN A monoclonal protein in serum or urme may indicate a malignant plasma proliferative process or monoclonal gammopathy of undeter- mined significance. ABSTRACT: Physicians not uncom- monly encounter patients with a mono- clonal protein in the serum or urine. Such paraproteins may indicate a seri- ous und er lying co ndition such as multi- ple myeloma or Waldenstr om 's macro- globulin emia, or may be a manifestation of a more benign monoclonal gam- mopathy of undetennined significance (MG US). However, up to 30% of patients with MGUS will ultimately de- velop a malignant disorder, so appro- priate clinical and laboratory follow- up is required. hen patients have routine serum elec- trophoresis or uri- nalysis, it is not uncommon to di s- cover monoclonal pro teins (al so known as paraproteins or M-prote in s) in the serum or urine. 1 ·3 Monoclonal proteins may also be discover ed as a result of the workup co mpleted for an inflam- mation or suspected infection. The key question to be answered whenever a monoclonal protein is identified in the serum or urine is whether or not this finding represents an unde rl y ing patho- logical process. J.4 Conditions that may be found in a patient with monoclonal protein include multiple myeloma, Waldenstrom 's macroglobulinemia, solitary plasmacytoma, extramedullary 382 BC M EDICAL JOURNAL- Volume 40, Number 9. Scpccmber 1998 plasmacytoma, ly mphoma, c hronic lymphocytic le ukemia, autoimmune disease, and carcinoma. Initial observa- tions in the 1970s found an incidence of age-related serum monoclonal parapro- teins of0.7% to 1. 2%. 3 Age has consis- tently represented an important vari- able; in one study 10% of patients older than 80 years had an M-prote in , while in another investigation 23% of patients aged 75 to 84 were found to have an M- protein. 5·6 As more sensitive assays were developed, even more individuals with monoclonal gammopathies were found. However, the majority of para- proteins found b-y these sensitive says were of low co n centra ti on. In one recent study more than 80% of serum Dr Brigden is medical oncologist/hematologist at the BC Cancer Agency's Cancer Centre for the Southern Interior in Kelowna.