LC-MGUS. Once LC-MGUS is detected, first rule out AL-amyloidosis, light-chain deposition disease, or cast nephropathy. If no malignant state is present, repeat the FLC serum assay every 6 months with renal function tests. Idiopathic Bence Jones proteinuria and LC-MGUS have some overlap and both entities put patients at risk for developing MM or amyloidosis. It is not uncommon for MGUS to be accompanied by Bence Jones proteinuria.
Likelihood of SMM progression varies with the combination of 3 factors: bone marrow plasmacytosis ≥10%, a serum M-protein level ≥3 g/dL, and a serum FLC ratio ≤0.125 or ≥8.
In addition to a thorough history and physical examination, recommended followup for both of these entities includes CBC, creatinine, serum FLC, and 24-hour urine protein electrophoresis.6 With idiopathic Bence Jones proteinuria, a monoclonal protein evident on urine protein electrophoresis at >500 mg/24 hr must be followed up with tests for other signs of malignancy (CRAB) and BM examination to exclude the possibility of MM.6
Treatment of MGUS to prevent progression
Multiple myeloma is still an incurable disease. Since MGUS is a precursor of MM, attempts have been made to either slow its progression or eradicate it. Several independent intervention studies26 for the precursor diseases MGUS and SMM have been conducted or are ongoing. Thus far, no conclusive preventive treatment has been found and the 2010 IMWG guidelines do not recommend preventive therapy for MGUS and SMM patients by means of any drug, unless it is a part of a clinical trial.1
CASE › The patient profiled at the start of this article has one abnormal risk factor (IgM isotype) and has a low risk of progression to MM. Management should follow the steps outlined in the ALGORITHM1,18 for low-risk IgM MGUS: repeat SPE, CBC, and CT scan in 6 months and annually thereafter. If any abnormality is observed, rule out the possibilities of IgM SWM, IgM WM, or rapid progression to MM, and consider referral to an oncologist.
CORRESPONDENCE John M. Boltri, MD, Department of Family and Community Medicine, Northeast Ohio Medical University, College of Medicine, 4209 St. Rt. 44, PO Box 95, Rootstown, Ohio 44272; jboltri@neomed.edu.
ACKNOWLEDGEMENTS The authors thank Kenneth F. Tucker, MD (Webber Cancer Center, St John Macomb-Oakland Hospital, Warren, Mich) and Elizabeth Sykes, MD (Professor, Oakland University, William Beaumont School of Medicine, Rochester, Mich) for their review of this article.
