Prevalence of Reduced Bone Mineral Density in Patients with Anti-neutrophil Cytoplasmic Antibody Associated Vasculitis and the Role of Immunosuppressive Therapy: A Cross-Sectional Study

Abstract:

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a relapsing-remitting disease, which is treated with corticosteroids (CS) in combination with cyclophosphamide. One of the major side-effects of this treatment is osteoporosis, which may result in the increased occurrence of fractures. In the present study we measured the prevalence of reduced bone mineral density (BMD) in a cross-sectional cohort of patients and correlated BMD findings with cumulative doses of CS and/or cyclophosphamide. BMD was measured by dual-energy X-ray absorptiometry (DXA) of the lumbar spine, radius and proximal femur between January 1998 and December 1999. Cumulative doses of CS and cyclophosphamide were calculated by chart review. Ninety-nine consecutive patients (48 men, 51 women) aged 55 ± 16 years (mean ± SD) were studied 50 months (median; range 0–400 months) after a diagnosis of ANCA-associated vasculitis had been made. Sixty-nine patients were treated with 10.7 g (median cumulative dose; range 0.4–67.2g) of CS, and 88 patients were treated with 34.1 g (median cumulative dose; range 0.8–324.3g) of cyclophosphamide. Fifty-seven percent of the patients had osteopenia (T-score: –1 to –2.5 SD), and 21% had osteoporosis (T-score: <−2.5 SD) at least at one site. Thirty-four of 37 (92%) postmenopausal women, 9 of 14 (64%) premenopausal women, and 34 of 48 (71%) men had either osteopenia or osteoporosis. The mean age- and sex-adjusted BMD (Z-score) of the proximal femur in men was found to be significantly lower than zero. Cumulative dose of CS therapy showed an inverse relation with Z-scores at the lumbar spine (p= 0.035) and proximal femur (p = 0.011). Cumulative dose of cyclophosphamide was not correlated with Z-scores. Osteopenia and osteoporosis are thus frequently observed in patients with ANCA-associated vasculities. However, only in men is the mean Z-score significantly lower than zero. Cumulative dose of CS therapy is significantly associated with bone loss at the spine and femur.