The risk of venous thromboembolic disease in patients with monoclonal gammopathy of undetermined significance

Background: Recent evidence indicates that patients with multiple myeloma receiving combination chemotherapy containing thalidomide are at a significantly high risk for venous thromboembolic disease (VTD). However, information on the occurrence of VTD in a related disorder, benign monoclonal gammopathy of undetermined significance (MGUS), is limited. Patients and methods: We prospectively investigated patients with MGUS for the occurrence of VTD. The diagnosis of MGUS was based on well known criteria for the disorder. The variables examined were sex, age, race, presence of underlying conditions, level and type of immunoglobulin [serum monoclonal (M)-protein] platelet counts and level of fibrinogen. Results: Of a total of 310 patients with MGUS, 19 (6.1%) developed VTD after a median follow-up of 44 months (range 12-67 months). In a univariate analysis, age,65 years (P=0.01), M-protein greater than or equal to16 g/l (P=0.001) and progression to plasma cell or lymphoproliferative disorders (28 of 310 patients; P=0.001) were significant risk factors for VTD. In multivariate analysis, M-spike greater than or equal to16 g/l [risk ratio (RR)=6.3; 95% confidence interval (0) 2.25-17.6; P=0.001] and future development of plasma cell or lymphoproliferative disorder (RR = 4.2; 95% CI 1.64-10.7; P = 0.003) were variables strongly associated with the occurrence of VTD. A total of 46 patients (14.8%) died during the follow-up period of the study. Conclusion: This study demonstrates that patients with MGUS are at increased risk for VTD. Although a clear reason for the pre-thrombotic state in these patients is not currently evident, few risk factors were identified in the group of patients examined.