[Epidemiology and prognostic aspects of ankylosing spondylitis]

The spondyloarthritides (SpA) comprise ankylosing spondylitis (AS), psoriatic SpA (PsSpA), reactive SpA (ReSpA), arthritis associated with chronic inflammatory bowel disease (SpAIBD) and undifferentiated SpA (uSpA). There are characteristic clinical features of SpA: inflammatory back pain (IBP), asymmetric peripheral arthritis, enthesitis, anterior uveitis, positive family history and others. The SpA, mainly AS, are strongly associated with HLA B27. AS is the most frequent and potentially most severe subtype, next to PsSpA. The prevalence of all SpA is rather high and not much different from rheumatoid arthritis (RA) and AS patients carry a burden of disease similar to RA patients. The prognosis of AS has not been extensively studied but some factors have been identified. There is a clear role for imaging modalities in the diagnosis of AS. Changes in the sacroiliac joint as detected by radiography still constitute the basis for the diagnosis of AS (New York criteria 1984). A diagnosis of sacroiliitis as made by magnetic resonance imaging (MRI) provides more objective evidence to a diagnosis of IBP arguing in favour of SpA which is defined on the basis of the ESSG criteria 1991 mainly on a clinical basis. Radiographic spinal changes such as syndesmophytes are important for the staging and outcome of AS. MR based assessment of spinal changes in are now being increasingly used to assess disease activity of AS patients. The presence of spinal radiographic changes at time of presentation was found to be the best predictor of further deterioration using the score modified SASSS' in a recent study. Other clinical features such as hip arthritis, early onset of disease, dactylitis, oligoarthritis, limitation of spinal mobility and poor efficacy of nonsteroidal antiinflammatory drugs were found to also have negative prognostic value.