Ankylosing spondylitis

Ankylosing spondylitis (AS) affects 0.2–0.5% of the northern European population, the prevalence varying with the prevalence of HLA-B27. It is a member of the spondyloarthropathy family and affects men three times more often than women. Symptoms usually begin in the third decade of life with inflammatory spinal pain. The key pathological element is enthesitis, though the main diagnostic feature is sacroiliitis. Approximately one-third of patients develop peripheral lesions including lower limb oligoarthritis, heel enthesitis, iritis, inflammatory bowel disease and psoriasis. Vertebral osteoporosis is not uncommon and cardiovascular disease and renal impairment may complicate severe AS. The diagnosis of AS is based on the modified New York criteria but criteria for early diagnosis, based on the co-occurrence of inflammatory spinal pain and demonstration of sacroiliitis by magnetic resonance scanning, are emerging. The cause(s) of AS remain unknown. Genetic factors, including HLA-B27 and the IL-23 receptor, confer susceptibility to AS but environmental precipitating factors have not been identified. Treatment involves the maintenance of spinal movement and comfort through exercise, supported, where necessary by analgesia and anti-inflammatory treatment. Disease-modifying anti-rheumatoid drugs are not effective for spinal disease but TNF-α inhibitor drugs provide dramatic improvements in symptoms, function and quality of life.