Patients with ankylosing spondylitis show individual patterns of variation in disease activity.

Disease activity was monitored sequentially over 1 year in 22 patients with ankylosing spondylitis (AS) attending regularly the local NASS group. Assessments, using standard methods, were made at monthly intervals by the same observer. There was marked heterogeneity such that each patient's profile of disease activity was virtually unique. All patients experienced at least one exacerbation and most underwent exacerbations and remissions, reminiscent of the experience of many patients with rheumatoid arthritis. In most instances no reason for changes in disease activity could be discerned clinically. These observations raise the possibility that the natural history of disease in AS may be different for each individual patient, which, if true, would have important implications for the design of studies to test the efficacy of therapy and for approaches to investigating pathogenic mechanisms in patients with AS.