Deep vein thrombosis after monoclonal gammopathy of undetermined significance and multiple myeloma

Patients with multiple myeloma ( MM) have an increased risk of deep venous thrombosis (DVT), particularly when treated with immunomodulatory drugs. Recently, 2 small hospital-based studies observed persons with the MM precursor condition, monoclonal gammopathy of undetermined significance (MGUS), to be at increased risk of developing DVT. Among 4 196 197 veterans hospitalized at least once at US Veterans Affairs hospitals, we identified a total of 2374 cases of MGUS, and 39 272 persons were diagnosed with DVT ( crude incidence 0.9 per 1000 person-years). A total of 31 and 151 DVTs occurred among MGUS and MM patients, respectively ( crude incidence 3.1 and 8.7 per 1000 person-years, respectively; P <.01). Compared with the entire study population, the relative risk (RR) of DVT after a diagnosis of MGUS and MM was 3.3 (95% confidence interval [CI], 2.3-4.7) and 9.2 ( 95% CI, 7.9-10.8), respectively. The most prominent excess risk of DVT was found during the first year after diagnosis of MGUS ( RR = 8.4; 95% CI, 5.7-12.2) and MM ( RR = 11.6; 95% CI, 9.2-14.5). Among 229 MGUS cases (9.5%) that progressed to MM, only one person had a DVT diagnosis before transformation. Our findings suggest the operation of shared underlying mechanisms causing coagulation abnormalities among patients with MGUS and MM. (Blood. 2008; 112: 3582-3586)