Bones and joints

Ankylosing spondylitis (AS) is an autoimmune-mediated subset of spondyloarthropathies, predominantly affecting young people, presenting at around 26 years of age with a male:female ratio of 2:1. The overall prevalence is between 0.1% and 1.4% (in mid-Europe 0.3%–0.5%) and the incidence between 0.5 and 14 per 100,000 population per year. About 80% develop the first symptoms before 30 years and less than 5% present at older than 45 years. Approximately 90%–95% patients are positive for HLA B27, and the risk of this disease developing is approximately 2%–5% in HLA B27-positive individuals and higher in HLA B27-positive individuals with a family history of spondyloarthopathy. However, most individuals who are HLA B27-positive remain healthy.