RESUMEN
BACKGROUND: To determine the bone mineral density (BMD), serum soluble receptor activator of the nuclear factors kappa B ligand (sRANKL) and the osteoprotegerin (OPG) levels in patients with ankylosing spondylitis (AS), and to determine their relationship with disease activity indexes. METHODS: The disease activity was evaluated by the Bath Ankylosing Spondylitis Disease Activity Score Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Metrology Index (BASMI) and Bath Ankylosing Spondylitis Patient Global Score (BAS-G). The BMD was measured by dual energy X-ray absorptiometry. Serum levels of sRANKL and OPG were measured by the sandwich enzyme-linked immunosorbent assay. RESULTS: Osteoporosis and osteopenia of the femoral neck were found in 33% and 41%, respectively. BMD of femoral neck showed a negative correlation with disease activities. The serum levels of sRANKL were higher in patients with AS than in controls, and the ratio of sRANKL to OPG was also elevated in AS, but had no correlation with disease activity. The sRANKL/OPG ratio tended to be higher in patients with lower BMD. CONCLUSIONS: BMD was reduced in 79% of AS patients and reflected disease status. The sRANKL/OPG ratio was upregulated in patients with AS and it appears to be related to BMD and radiological changes. These results suggest that the imbalance between RANKL and OPG might be involved in the pathogenesis and clinical courses of AS.