Osteoporosis in rheumatoid arthritis

OBJECTIVE: To quantify the magnitude and distribution of osteoporosis in rheumatoid arthritis (RA). METHODS: Bone mineral density (BMD) was measured by dual x-ray absorptiometry, in a monozygotic co-twin control study. RESULTS: BMD was reduced at most skeletal sites in the twin with RA compared with the co-twin (lumbar spine 4.6%, femoral neck 9.7%, total body 5.7%). Differences in lean soft tissue (5.6% for total body) correlated with differences in BMD between twins at multiple sites. CONCLUSION: Osteoporosis in RA is generalized and may be related to loss of mobility or muscle mass associated with the disease.