Lumbar bone mineral density as the major factor determining increased prevalence of vertebral fractures in monoclonal gammopathy of undetermined significance

The possible relationships between biochemical measurements and both densitometric and radiographic indexes of skeletal fragility were evaluated in 65 postmenopausal women with monoclonal gammopathy of undetermined significance (MGUS). There was a significantly higher prevalence of vertebral fractures in the MGUS group compared with a control population (P <= 0.001). The MGUS patients were then grouped according to the presence or absence of at least one mild vertebral fracture. Patients with fractures (Fx, n = 34) were older (62.8 +/- 6.1 years), with long-standing disease (8.8 +/- 7.1 years) when compared with those without fractures (NFx, n = 31; 59.7 +/- 5.0 years, P <= 0.05 and 5.8 +/- 4.1 years, P <= 0.05). The receptor activator of nuclear factor kappa-B ligand/osteoprotegerin ratio was higher in Fx compared with NFx (0.092 +/- 0.018 vs. 0.082 +/- 0.020; P <= 0.05). Lumbar spine (0.811 +/- 0.14 vs. 0.956 +/- 0.12 g/cm(2)), femoral neck (0.660 +/- 0.09 vs. 0.747 +/- 0.10 g/cm(2)) and total bone mineral density (BMD) (0.788 +/- 0.11 vs. 0.884 +/- 0.11 g/cm(2)) were lower (all P <= 0.001) in Fx-MGUS compared with Nfx patients. Receiver operating characteristic curves identified lumbar BMD as the variable that best predicted vertebral fractures (area under the curve 0.817; 95% confidence interval, 0.713-0.921). This study provides an indication for the measurement of BMD in MGUS patients, as a means of predicting vertebral fractures, especially in those that are asymptomatic. Patients with prevalent fractures should undergo pharmacological treatment to prevent further fractures.