Mean BMD of the group with BMI < 18.5 (kg / m2) was lower than that with BMI ≥ 18.5 (kg / m2) (p<0.05). Patients with less than the 2-year duration of the disease had higher BMD at both lumbar spine and femoral neck than those with disease duration of 2 - 5 years or more than 5 years; the later the disease stage was, the more reduction the BMD was (p<0.05).