Aortic calcification contributing to bone densitometry measurement

A 75-yr-old glucocorticoid-dependent asthmatic male had a bone mineral dens ity study to assess possible osteoporosis prior to initiating therapy. A ra diograph of the lumbar spine revealed an asymmetrical compression of the se cond lumbar vertebra, marked scoliosis, vertebral osteopenia, and a highly calcified abdominal aorta. Bone mineral density (dual X-ray absorptiometry [DXA]) revealed low bone mass in L2-L4 and a markedly abnormal pattern, wit h a linear central density representing a calcified aorta. Posterior-anteri or measurements of the midlumbar region with and without the overlying aort a indicated that the calcified vessel contributed up to 33% of the measured density. This was a far higher contribution than reported in other studies . Lateral DXA measurements of the L2 vertebra and the overlying aorta were performed to validate this finding. The density of the L2 vertebra was 0.21 5 g/cm(2), and that of the overlying calcified aorta was 0.210 g/cm(2) This case suggests that aortic calcifications may contribute significantly to o verall lumbar bone density and, unless recognized, can inadvertently lead t o misclassification of osteoporosis.