Osteoporosis and rheumatic diseases.

Numerous rheumatic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, psoriatic arthritis, ankylosing spondylitis, systemic lupus erythematosus, systemic sclerosis, dermatomyositis/polymyositis and vasculitis are characterized by osteoporosis and fragility fractures. Inflammatory cytokines, glucocorticoid treatment, immobilization and reduced physical activity due to painful joints and muscle weakness are considered the main risk factors that cause low body mass density values in these diseases. Emerging evidence highlights the role of inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1, IL-6, IL-7 and IL-17, in the regulation of the bone homeostasis. In fact, chronic inflammation is often characterized by an imbalance between bone formation and bone resorption with a net prevalence of osteoclastogenesis, which is an important determinant of bone loss in rheumatic diseases.